Where does “Ọṣun” come from?

Ọṣun (Yoruba) comes from Proto-Mongolic -sun — Noun-forming suffix.

Ọṣun (Yoruba): Oshun, an orisha in Yoruba religion, she is regarded as the Yoruba deity of fertility, freshwater, love, beauty, motherhood, healing, and jewelry, and is the spirit of the Osun river