Probably an affectionate alteration of mama or reduplication of mother.
The word Ma Maw is termed as a slang word, derived from Glasweegian Strathclyde Gaelic Scots. Ma is used when addressing ones own Mother, Maw is used when addressing others of ones own or others mothers ( aye yer maw, Glaswegian humour inferring disbelief with a hint of ridicule) Ma is also used to mean what is with you, what is beside you ( inferring ownership) when using both together, Ma Maw translates to My Mother.
mamaw (plural mamaws)
- UK `dialect `Scottish lowlands` one's mother.
- (US, dialect, Southern US) One's grandmother, especially one's maternal grandmother.
- (US, dialect, Southern US, less commonly) One's mother.