1084: Yiddish and German Nov 27, 2017

The most similar language to English is generally said to be Frisian, specifically West Frisian. Still, if an English speaker heard West Frisian for the first time, he or she not likely understand what was being said, because even though they share the Ingvaeonic root (see photo below*) there are still many centuries of foreign influence and geographic isolation that made the two languages distinct. Because they are both so famous, and because they are spoken quite near to each other, one might assume that the most similar language to Modern German would be Dutch, and while the two are certainly quite similar to the point that there is some level of mutual intelligibility (though not 100% or anywhere close to that) Yiddish is actually closer related. Though German and Yiddish occasionally differ in some vocabulary, accent, and word-order, they are remarkably similar, in part because the two only diverged relatively recently, and were spoken in a similar region.

*http://yiddish.biz/