At some unknown point in the fifteenth century, we borrowed the French term jean fustian into English to describe a trendy new cotton-based fabric. Later, the fustian was dropped, as it was cumbersome. So your jeans come to you from jean fustian. What the heck is that, though? Well, fustian is just a word for "fabric", and it's not essential to the formation of the word jeans, so just forget that. But the first part of the term, jean, is a modern spelling of Jannes, which is an Old French spelling of Genoa, the Italian city name. This is because Genoa was one of the cities where the fashion emerged. In fact, the later pluralization of jeans from jean is based on Jannes, that Old French spelling. Yes, language is a mess. But it's serendipitously beautiful too: by pure coincidence, the city name of Genoa comes from the Proto-Indo-European root gnewo, meaning "knee", through Ligurnian (based off geographical position). How weird is it that the kind of pants so many people wear is named after a city named after a knee?
Adam Aleksic, a freshman studying linguistics at Harvard University, has been described as the internet's sixth most famous etymologist. He has disturbing interests in words, vexillology, geography, board games, limericks, and law, and he loves writing about himself in the third person.
The Etymology Nerd