I don't know; I only knew ndege. (Oh, I should have checked my dictionary last night. Will do so tonight if I remember.) Trying to filter copycat word-lists out of on-line search suggests nyuni might be 'archaic' (The Kamusi Project seems fairly solid) (and the ordinary word in some related languages), but don't quote me. FWIW nyuni doesn't occur in the Swahili Wikipedia.