Today, I mostly associate the word gregarious with outgoing people, but when it was first borrowed into the English language in a 1668 essay, it was a biological term used to describe animals that live in flocks (this is still used in zoology, and, in botany, it refers to plants that grow in clusters). It comes from Latin gregarious, meaning "of or pertaining to flocks". This was the adjectival form of grex, the word for "flock" or "herd", and that finally derives from the Proto-Indo-European reconstruction hger, meaning "assemble" or "gather". Grex is also the etymon of the words aggregate ("to collect the flock"), congregate ("with the flock"), segregate ("apart from the flock"), and egregious ("out of the flock"); the latter might shed some insight into why it's so commonly confused with gregarious.
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.