nance n.

"effeminate man, male homosexual who takes the passive role," 1924, from female name Nancy (q.v.), which was in use as an adjective meaning "effeminate" (applied to men) by 1904 in prison slang, a shortening of earlier Miss Nancy, a derogatory term for a finicky, effeminate man which is attested by 1824; Nancy boy "effeminate male homosexual" is attested by 1939. 

Nancy, Miss, an opprobrious epithet for an exceedingly effeminate, over-nice young man. The original Miss Nancy, however, was a Mrs. Anna Oldfield, a celebrated actress, who died in 1730 and was buried in Westminster Abbey. She was extremely vain and nice about her dress, and as she lay in state, attended by two noblemen, she was attired, as she had directed shortly before her death, in "a very fine Brussels lace head-dress, a Holland shift with a tucker and double ruffles of the same lace, a pair of new kid gloves," etc., a circumstance alluded to by Pope .... [William S. Walsh, "Handy-Book of Literary Curiosities," 1892]

Walsh's proposed origin might not be exact. Related: Nancified.