"deliberately unintelligible speech," by 1938, from double (adj.) + talk (n.). Old English had a similar formation in twispræc "double speech, deceit, detraction." An analysis of Chinook jargon from 1913 lists mox wawa "a lie," literally "double talk."

Latin, hic iacet, "here lies," commonly the first words of Latin epitaphs; from demonstrative pronominal adjective of place hic "this, here" + iacet "it lies," third person singular present indicative of iacēre "to lie, rest," related to iacere "to throw" (from PIE root *ye- "to throw, impel").