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.

   If you double-cross us, we'll track you down and kill you.

2. (plant breeding, animal breeding) To cross twice in hybridization, as (A × B) × (C × D); for example, in commercial hybrid seed corn, A through D are classically inbreds, and their grandoffspring is the seed for sale.

• double-crosser

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