double-cross

First recorded in 1834 from thieves' slang cross (or on the cross) to refer to something dishonest, a play on straight/square, and therefore a crook going back on his partners would be crossing the crossers, or double-crossing.

double-cross (third-person singular simple present double-crosses, present participle double-crossing, simple past and past participle double-crossed)

1. To betray or go back on

• “Double-cross” in Michael Quinion, Ballyhoo, Buckaroo, and Spuds: Ingenious Tales of Words and Their Origins, Washington, D.C.: Smithsonian Books in association with Penguin Books, 2004, →ISBN.