Happy new year and all that! 2017 is a prime-numbered year, and I wanted to usher it in with the etymology of the word prime. The farthest back that it can be traced is the word per, which everybody agrees was the Proto-Indo-European word for "before". Various sources of mine also list it as "forward", "before", and "through". In any case, in one form it meant "antecedent", and was antecedent to the Proto-Italic priisemos, which was kind of an objectively adjectival form of the former (I'm having way too much fun with English right now). This changed to prisemos, then merely to prismos, which jumped a rung into Latin and the word primus. This meant "first", specifically, but could be applied figuratively to one in power. Primus also gave us the Spanish and Portuguese word primo, meaning "cousin", and the false cognate in Italian and Esperanto, where primo meant "prime number" only. After a short time in French, it became the English word "prime", which meant "first" as well. This loitered around a while (spawning the verb "to prime") until it got picked up by mathematics, where a prime number is the first multiple of itself.
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