nun (n.)

"children's nurse," 1795, from the widespread child's word for "female adult other than mother" (compare Greek nanna "aunt," and see nana). The word also is a nickname form of the fem. proper name Ann, which probably is the sense in nanny-goat "female goat" (1706, compare billy-goat). Nanny-house "brothel" is slang from c. 1700. Nanny state, in reference to overintrusive government policies is attested by 1987, the term is associated with British political leader Margaret Thatcher, who criticized the tendency. Nannyism in reference to actions or policies considered unduly protective is by 1959; also compare the verb.

late 13c., nonnerie, "nunhood, the life of nuns," from nun + -ery or from Old French nonnerie. Meaning "convent or cloister for the exclusive use of nuns" is from c. 1300. Transferred meaning "house of ill fame" is attested by 1590s.