Dishonest

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late Middle English (in the sense ‘dishonourable, unchaste’): from Old French deshoneste, Latin dehonestus .

wiktionary

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From Middle English dishoneste(“dishonourable”), from Old French deshoneste, from Latin dehonestus. Synchronically, dis- +‎ honest.

etymonline

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dishonest (adj.)

late 14c., "disgraceful, shameful, without honesty or integrity; unjust, unfair, disposed to deceive or cheat; unmodest, unchaste," from Old French deshoneste (13c., Modern French déshonnête) "dishonorable, horrible, indecent," perhaps from a Medieval Latin or Gallo-Roman compound of Latin dis- "not" (see dis-) + honestus "honorable; deserving honor, respectable," from honos "honor, dignity, office, reputation," which is of unknown origin. The Latin formation was dehonestus. Related: Dishonestly.