mumma vs mammy

mumma and mammy both are nouns.

Word	Noun	Adjective	Verb	Adverb
mumma	Yes	No	No	No
mammy	Yes	No	No	No

As nouns, mumma and mammy are synonyms defined as:

Other synonyms of mumma include ma, mama, mamma, mom, momma, mommy, mum, mummy.

mumma (noun)	mammy (noun)
informal terms for a mother	informal terms for a mother
	an offensive term for a Black nursemaid in the southern U.S.