Green’s Dictionary of Slang

to mention; usu. in phr. don’t mensh, don’t mention it.

1889		Nat. Police Gaz. (NY) 28 Dec. 6/1: There are things, / Oh, there are things / ’Twere better not to menching.
1909		Pearson’s Mag. 21:4 439: ‘That’s very kind of you.’ ‘Don’t mensh.’.
1911		Gem 9 Dec. 16: Don’t mench, dear boy!
1917		A. Brazil Madcap of the School 176: Raymonde bowed [...] ‘Don’t mensh! Glad to do my bit!’.
1922		G.A. Milton Fugitive Millionaire 21: Don’t mensh. I understand my dear.
1947		J. Maclaren-Ross Of Love And Hunger 138: ‘Thanks a lot.’ ‘Don’t mench.’.
1954		E. Hunter Blackboard Jungle 105: ‘You got a keen analytical mind.’ ‘Thank you,’ Rick said. ‘Don’t mensh it.’.