Single Word Requests – Word for a Person Who Is Both Female and Your Friend

To take one of your examples, doe is from old English deon, to suck, and was used to describe a female animal of a number of kinds. buck is from old English bucca, a he-goat. The unisex rabbit is from Flemish. So the words buck and doe appear originally to have meant the male and female of any animal, and have presumably become specialised in referring to deer, rabbits, and certain other kinds of animals.

Ram and sheep are both derived from old English, in the case of ram a word meaning fighting sheep. (Ewe is from Latin.) I'd hazard a guess that in old England there were fighting sheep (males) and sheep (all the others, including wethers).

Hope this helps (all this from the Collins English Dictionary, except the suppositions and guesswork).

Certainly acquaintance would be my own choice, but perhaps you found something remiss with it.

You might further qualify it by saying something like casual acquaintance, incidental acquaintance, nodding acquaintance, or long-time acquaintance.

Of those, I rather like nodding acquaintance, since it implies that this is someone whom you would nod to in passing, but not pause and chatter at.