Where does “Nancy” come from?

I cannot write this summary because the etymological chain provided is circular and repetitive (cycling through Anne, Ann, and annual without progressing to older languages), contains no information about the origin of Nancy specifically, and provides no known meaning to work with. A reliable etymology requires a linear chain showing actual language-to-language development with at least one attested source language.

Nancy (English): An effeminate man, especially a homosexual