When someone refuses to pay a bet, we say that they have welched on it. This expression originated in the 1860s in English horse racing slang and very likely is an insult geared towards Welsh people, which resulted from the xenophobic mistrust of the people-group by the English. This ethnic tension hails all the way from the 400s CE, when the Anglo-Saxons, Jutes, and other Germanic invaders began displacing the Celtic tribes in what is now England. Their word for the Welsh, Wealh, literally meant "foreigner", despite the fact that they were, ironically, the natives of the land. Wealh comes from the Proto-Germanic word walhaz, which could refer to any Celtic group but earlier on was specific to the Volcae people, who probably had a name meaning something like "hawk" in Proto-Celtic.
Hello! I'm Adam Aleksic, a sophomore studying government and linguistics at Harvard University, where I co-founded the Harvard Undergraduate Linguistics Society. In addition to etymology, I also really enjoy politics, vexillology, geography, board games, conlanging, and law.