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1610s, "insufficient," from French incompétent, from Late Latin incompetentem (nominative incompetens) "insufficient," from in- "not" (see in- (1)) + Latin competentem (see competent). Sense of "lacking qualification or ability" first recorded 1630s. The noun meaning "incompetent person" is from 1866. Related: Incompetently.
incompetent in·com·pe·tent (ĭn-kŏm'pĭ-tənt)
Inadequate for or unsuited to a particular purpose or application.
Incapable of proper functioning.
Not qualified in legal terms.