I always thought that the north Indian name nitu or neetu was short or pet forms of names with nitya (or one of its derived forms) as an element. nitya ultimately comes from ni (cognate with the roots in English beneath and nether) meaning down, into or within, and whose derivatives seem to suggest a meaning of own (e.g. nija from jan to be born means `born within' or innate, and is the common word for one's own). nitya is a very old word also meaning innate or one's own, but the meaning that most people will recognize today is invariable. permanent, or indispensible.