"dupe, saphead," rogues' slang from late 16c., perhaps a shortening of cullion "base fellow," originally "testicle" (from French couillon, from Old French coillon "testicle; worthless fellow, dolt," from Latin coleus, literally "strainer bag;" see cojones), though another theory traces it to Romany (Gypsy) chulai "man." Also sometimes cully, though some authorities assert cully was the canting term for "dupe" and cull was generic "man, fellow," without implication of gullibility. Cf. also gullible.
c.1200, originally "put through a strainer," from Old French coillir (12c., Modern French cueillir) "collect, gather, pluck, select," from Latin colligere "gather together, collect," originally "choose, select" (see collect). Related: Culled; culling. As a noun, from 1610s.