Perhaps Phil was a spy, working at Gagosian but secretly in the employ of White Cube. Actually, now that the idea of duplicity had entered Jeff's mind, it occurred to him that his gallery was having a party to which Jeff had been conspicuously uninvited.
-- Geoff Dyer, Jeff in Venice, Death in Varanasi
Here on the beach under a good sun Hiro-matsu forced himself into a polite bow, hating his own duplicity.
-- James Clavell, Shogun
It didn't occur to him that Laura might have had an ulterior motive in seeking him out. Laura had a direct gaze, such blankly open eyes, such a pure, rounded forehead, that few ever suspected her of duplicity.
-- Margaret Atwood, The Blind Assassin
Duplicity comes from Middle English duplicite, from Old French, from Late Latin duplicitās, doubleness, from Latin duplex, duplic-, twofold.