Green’s Dictionary of Slang

(Aus./N.Z.) a phr. used to indicate one’s lack of interest/dismissal of an idea or thing.

1918		Kia Ora Coo-ee 15 Oct. 4/2: But the pick of the bunch [of WWI coinages] is ‘maleesh’: a whole philosophy in seven letters [...]. What do you think? It’s a good philosophy for life’s little ironies; only, don’t apply it to greater matters.
1925		(con. WWI) Fraser & Gibbons Soldier and Sailor Words 151: Maleesh: (Arabic). Never mind. It doesn’t matter.
1945		J. Henderson Gunner Inglorious (1974) 117: Come on, let’s cut the lot. Here’s my packet. Maleesh domani.
1968		G. Slatter Pagan Game (1969) 163: Maleesh the condys — I’m a monty for the big double, Saturday.
1977		(con. 1941) R. Beilby Gunner 285: Maleesh the condys, Abdul!