We don't have synonyms for minny yet — it may be a rare, specialized, newly coined, or misspelled word. The closest thesaurus entries we have are ninny, tinny and mingy.
(n) :
(US, slang) Alternative form of Minnie (“Minneapolis”). [A diminutive of the female names Wilhelmina, Minerva, Mary, Mina, Mamie and Hermione. Popular as a formal female given name in the 19th century.]
(n) :
(US, slang) Alternative form of Minnie (“Minneapolis”). [A diminutive of the female names Wilhelmina, Minerva, Mary, Mina, Mamie and Hermione. Popular as a formal female given name in the 19th century.]