Where does “ūnanimus” come from?

ūnanimus (Latin) comes from Latin ūni-, from Latin ūnus, from Old Latin oinos, from Proto-Italic oinos, from Proto-Indo-European óynos — one; single.

ūnanimus (Latin): concordant, harmonious, unanimous (that acts as one), in concert, of one mind, like-minded, one-souled, sympathizing