We don't have synonyms for massah yet — it may be a rare, specialized, newly coined, or misspelled word. The closest thesaurus entries we have are mastah, massa and massar.
(n) :
(US, historical, colloquial) Pronunciation spelling of master, representing African-American Vernacular English. [Someone who has control over something or someone.]
(n) :
(US, historical, colloquial) Pronunciation spelling of master, representing African-American Vernacular English. [Someone who has control over something or someone.]