The Collaborative International Dictionary of English v.0.48:
mammy \mam"my\ (m[a^]m"m[y^]), n.; pl. mammies (m[a^]m"m[i^]z). A child's name for mamma, mother. [1913 Webster]WordNet (r) 3.0 (2006):
mammy n 1: an offensive term for a Black nursemaid in the southern U.S. 2: informal terms for a mother [syn: ma, mama, mamma, mom, momma, mommy, mammy, mum, mummy]