genteel

Borrowed from French gentil ("gentile"), which came from Latin gentīlis, meaning "of or belonging to the same people or nation." That word traces back to Latin gēns, meaning "clan, tribe, people, family."

The facts given don't trace how the sense shifted from tribal belonging to refined manners, so the safest thing to say is that it entered English through French as gentil and settled into its current spelling and meaning as "genteel."

It's a doublet of gentle, gentile, and jaunty — all four words descend from the same Latin root but arrived in English by different paths.