1591: bellwether Apr 23, 2019

Some words have etymologies that require knowledge of other languages and phonology to understand, while others may be surprising simply because other related words fell out of fashion. In the case of 'bellwether', the word is usually used to mean a predictor of something, but it can also mean the goat that leads the herd. Considering the second, less common usage of the word, it is easy to see why this is, a 'wether' is another term for a ram—though generally only a castrated one—and it wears a bell. If it were not for this other meaning, it would be yet another etymology drawn from goats and sheep that has no relation to them now.

1590: Productivity of Rhyming: hobby and robin Apr 22, 2019

The word 'hobby' comes from a name for a horse breed, that in turn came from a given name, that is also the name for a bird. That might sound a little confusing, but arguably nicknaming used to be much more popular, and this led to the creation of some words that outlived the nickname. 'Hobby', meaning a fun but not necessarily productive leisure activity comes from 'hobbyhorse': a toy horse that doesn't move anywhere. However, 'hobby', and 'dobbin—the older term for 'hobbyhorse—come from the given name 'Robin', which was originally short for Robert. Moreover, the bird 'robin' also comes as a pet form of the name Robert. This may seem weird, but compare it to other rhyming names like 'Dick', 'Bill', or 'Bob', and you'll see the popularity of the rhyming trend.

1589: burrito Apr 21, 2019

The now infamous 'burrito' is pretty recognizable these days, both in name and in image, but it got its name from something else. The word 'burrito' comes from the Spanish diminutive suffix '-ito' on 'burro', which means 'donkey'. There are some different ideas as to why this is, including having it loaded with different ingredients like a donkey with packs, but given that another name for the burrito in Spanish is 'flautas' ('flute'), there is a chance that both of those words were just a description of the shape in some way.
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1588: bawl and bark Apr 20, 2019

Words like 'wail', 'woe' and 'bawl' all have their roots as onomatopoeias, they do not imitate the same thing. 'Wail' comes from 'woe', and they both were originally imitation of people crying. 'Bawl' however was originally a description for the sound of dogs. It was only when the word was used, somewhat demeaningly, to relate the crying of people to dogs that the word now is predominantly used in relation to people. Indeed, this is similar to the word 'bark', which was today mostly denotes that of a dog, but originally meant any kind of explosive sound, even from people, and has its roots in onomatopoeia.

1587: arctic Apr 19, 2019

The word 'arctic' comes from the Greek word for 'bear', but this has nothing to do with polar bears. Instead, Ursa Major, aka the Big Dipper or literally the Great Bear is the constellation that can be seen northward in the night sky, and the northern part of the word was named for that. Indeed, while nowadays the word arctic described the northern region of the globe, 'arctic' a long time ago used to refer to that part of the night sky.
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1586: dandelion Apr 18, 2019

The word 'dandelion' today simply denotes a kind of flower, but it's name used to be a bit more complex. The word has always referred to a flower, but it used to connote a lion too. The name comes from the French 'dent-de-lion', a translation of the Latin 'dens lionis', meaning 'tooth of the lion'. The name referred to the jagged leaves, and did not relate to the mane as could be imagined.

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1585: Chicken and Fowl Apr 17, 2019

While the '-en' suffix of 'chicken' is diminutive, 'chicken' is not the small form of 'chick'. In fact, every type of baby bird is called a 'chick', and at no point was 'chicken' supposed to refer to a small baby bird. Indeed, this type of bird used to only be called a 'fowl', and then through a mostly random process through history had the name 'chicken' adopted for it.

1584: colt and filly Apr 16, 2019

These days 'colt' denotes young, especially male horses and 'foal' is the general term, both in terms of gender and even species, relating to related animals. It used to be somewhat reversed, insofar as 'colt' initially denoted 'young camel' or 'young donkey'. It is also related to the Norwegian 'kult' (tree-stump) as the root simply meant anything small and thick. It is also because of 'foal' that the related, feminine term 'filly' exists, although its pejorative uses are more contemporary. Support Word Facts on patreon.com/wordfacts

1583: heresy Apr 15, 2019

Free thought is usually prized in a modern democratic society, but from a time in history when this was not the case, there is still some effect on the lexicon. The word 'heresy' comes from the Greek 'haireomai' meaning 'choose'. Originally, this word and its various forms referred to a person taking a school of thought or sect of usually—but not necessarily—Christianity, but over time the word morphed to denote an idea that was not in line with a particular orthodoxy. Usually this word has religious contexts nowadays, but it is in some ways just as traditional when it is used to describe politics, for example.

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1582: addict Apr 14, 2019

It has been discussed here before how ‘addict’ backformed from ‘addicted’, and has its first recorded use in only 1909, but this is only scratching the surface of the history of this word. ‘Addicted’ comes from a Latin verb ‘addicere’ meaning ‘say to’ i.e. ‘dictate’, but would often mean something more like ‘assigned’, as in slavery. Indeed, eventually it came to refer to someone who was seen to be a slave not to a person so much but to a substance usually.

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1581: Crocodile Tears is in over 40 Languages Apr 13, 2019

Although we think of idioms as being fairly culturally specific, a calque for 'crocodile tears' exists in over 40 European languages, and even some outside Europe including in Swahili and apparently Mongolian. Part of the reason for this that there was a myth that crocodiles shed a tear when they ate their prey, but since this phrase had existed in Latin too, it disseminated the idea into other, modern languages. Crocodiles do actually have tears that are only for moisture and not emotion, so there is some truth behind it as well.

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1580: muscle Apr 12, 2019

The vast majority of medical or scientific terms come from either Latin or Greek in some form, and while these may be considered serious or official in English, this isn’t always the case for where the terms derive. The word ‘muscle’ comes from the word ‘mus’, the Latin word for ‘mouse’, with the rest of ‘musculus’ being a Latin diminutive suffix. Muscles were seen to look like little mice.

1579: malaria Apr 11, 2019

Throughout history, very little was known about medicine in the scientific way it is now, and this has made subtle lasting impressions on language. For instance, the word ‘malaria’ is a type of parasite transferred by mosquitos, and while in the past it was understood to come after being in swampy areas, it was thought to come from bad air quality. The word ‘malaria’ comes from a contraction of the Italian ‘mala aria’ (bad air). However, this wasn’t only just for bad medicine, as for a while around the 18th century, ‘malaria’ was simply used to describe any kind of swampy environment.

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1578: tragedy and tragic: a goat song Apr 10, 2019

There are many words for which the origin is unknown or too disputed for confidence, but less common is when the etymology is known but no one knows why. For instance, the word ‘tragedy’ comes from Greek—not surprising with the rich history of the Greek tragedy in drama—but when broken down the word translates directly as ‘goat song’, ‘tragōidia’ being from ‘tragos’ meaning ‘goat’ and ‘ōidē’, which also gave English ‘ode’. Indeed, ‘tragic’ was only associated to ‘tragedy’ in English much later, but in French and Greek again comes from this ‘tragos’, so even divorced from the ‘ode’, there is again the connection between goats and sorrow from Greek. 

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1577: loophole Apr 9, 2019

Today, a 'loophole' means a lapse or inadequacy in something that can be used taken advantage of, and while it meant much the same thing in the 16th century, the initial subject matter was not rules, but walls. In the historical sense, a loophole was a hole through a wall from which someone could fire an arrow. In the late 16th century, the word 'loop' also denoted a an embrasure, so while those may have fallen out of style architecturally, the phraseology has persisted.
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1576: daemon vs. demon Apr 8, 2019

'Daemon' today may just look like an older way of writing 'demon', and while there is some truth to that, it is much deeper. As with many English words with 'ae' or 'oe' representing only one sound, this word is from Greek. At that time, it could mean anything supernatural from 'deity' to 'lesser spirit', and this reflected somewhat in 'daemon', which still means 'divinity' or 'inner spirit'. The purely negative connotations came later, and are now denoted exclusively in 'demon', despite identical pronunciation. Indeed, 'demon' only became the popular way to write the word in the 19th century.

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1575: Zero-Marking Word Order Apr 7, 2019

It is true that languages that make less use of affixes and other morphological features tend to rely on the order of words to convey meaning more than others, the dependency on word order is sometimes more acute than this even. Languages without specific marking for possession, such as English's possessive S, tend to be arranged subject-verb-object. The theory behind this is that the way this tends to be solved in languages that do this such as Arabic is that the nouns are simply put next to each other in the sentence to show possession, and since at other times any two nouns would be separated by the verb, it makes it clear that there is a difference.

1574: cabal and kabbalah Apr 6, 2019

The word 'cabal', connoting secret societies, comes from 'kabbalah' (קַבָּלָה), i.e. Jewish mysticism, but this doesn't have to do with beliefs of Jewish conspiracies, at least not directly. Instead, it comes from the Old French 'cabale' which actually held both meanings together, but denoted more mildly 'private groups', and any mystical reading of the Old Testament. Both of those meanings evolved in English until they were were well and truly distinct, but in fairness and from a historical perspective, Kabbalah's influence in general peaked in the European Middle Ages, so there would have been some precedent for it. 
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1573: Losing and Regaining Z Apr 5, 2019

The letter Z comes from the Greek letter zeta (Ζζ), but for a while it was removed from the Latin script. In around 300 BC, the Censor Appius Claudius Caecus removed it from the Latin writing system; even when it was reintroduced 200 or so years later it was done so only for Greek loan words. There are many cases in which something is written with an S but the sound is voiced like [z], such as in 'wisdom', and often—though not always—this history is why. Germanic languages adopted the Z and use it a great deal, but Latin languages does not use the letter. 
Watch more about letter here: https://youtu.be/dntJLHmkfhw

1572: German Contractions Apr 4, 2019

There are plenty of contractions in English, but with a few exceptions these are centered around verbs. This is not so in German. In that case, while there are some contractions that involve verbs, some of the most common ones relate to articles—in English those are 'a' and 'the'— so that phrases like 'in das' meaning 'in the' (neuter) becomes 'ins', and 'in dem' also 'in the' (masculine) becomes 'im'. This happens to a number of other prepositions, such as 'an', 'hinter', 'um', 'vor' and so on, but not always consistently. For instance, 'zu der' becomes 'zur' in the feminine and 'zu dem' becomes 'zum' in the masculine and neuter, but 'zu den' only becomes 'den' dialectal varieties of German, such as in Berlin, but it is not considered standard. The reason for this is as much luck as anything else.

For more on dialects, watch this: https://www.youtube.com/watch?v=4CM7-BMO3vk&t=243s