Effective

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late Middle English: from Latin effectivus, from efficere ‘accomplish’ (see effect).

wiktionary

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From French effectif, from Latin effectīvus(“productive; effective”), from efficiō(“I make; I bring about”).

etymonline

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effective (adj.)

late 14c., "serving to effect the intended purpose," from Old French effectif, from Latin effectivus "productive, effective," from effect-, stem of efficere "work out, accomplish" (see effect (n.)). Of military forces, "fit for action or duty," from 1680s.