941: a- Jul 7, 2017

In terms of its vocabulary, English is something of a hodgepodge with large percentages coming from different languages, notably Latin, French, and Greek. It is for that reason that the prefix 'a-', which is used in four different ways, can come from four different languages. First, it can be added to words, usually adjectives, to mean 'not', such as 'atypical'; this comes from Greek. In other words such as 'asleep' or 'afoot' the prefix can be replaced fairly seamlessly with the preposition 'in' or 'on', and indeed this form of 'a-' derives from the Old English 'on'. The word 'aloft' has a similar prefix, but it is ultimately Old Norse, and only found as part of a few words specifically. Third, it can mean 'utterly'  such as with 'abash', deriving from the Old French 'es-' with the same meaning. Finally, 'a-' is sometimes found as a form of the Latin 'ad' meaning 'toward' such as in words like 'aspire'.