"children's nurse," 1795, from widespread child's word for "female adult other than mother" (cf. Gk. nanna "aunt"). The word also is a nickname form of the fem. proper name Anne, which probably is the sense in nanny goat (1788, cf. billy goat). The verb meaning "to be unduly protective" is from 1954. Nanny-house "brothel" is slang from c.1700.
[nan-ee] 
