negligent (adj.)

late 14c., necligent, of persons, "remiss, indifferent to duty," from Old French negligent "careless, negligent" (13c.) and directly from Latin negligentem (nominative neglegens) "heedless, careless, unconcerned," present participle of neglegere "to neglect" (see neglect (v.)). Of action, conduct, etc., c. 1500. Related: Negligently.