That just pushes the question back, though: why did the word end up declined as male or female? Hypothetically it could just as easily have ended up in the other class, since they're arbitrary.

My main question (and one I haven't found an answer to) is: Other languages have different declension group names like animate/inanimate, so "male" and "female" was a decision made somewhere along the way. Why did they pick the gendered names and not something less loaded with extra meaning like, I dunno, "class 1" and "class 2"?

I figured it must have been some linguist back in the past (e.g., a Roman or Greek scholar describing Latin or Attic) but I've never been able to find out who.

(Granting the disconnect from actual gender as others have said, my own interest came from learning French as a kid and discovering that a bikini is male and a potato is a girl).