Unlike

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Middle English: perhaps originally an alteration of Old Norse úlíkr ; compare with Old English ungelīc ‘not of the same kind, not comparable’.

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From Middle English unlic, unlich, from Old English unlīċ, unġelīċ(“unlike, different, dissimilar, diverse”), from Proto-Germanic *ungalīkaz; surface analysis: un- +‎ like. Cognate with Dutch ongelijk, German ungleich, Old Norse úlíkr(see there for North Germanic descendants).

From Middle English unliken, unlyken, equivalent to un- +‎ like.

etymonline

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unlike (adj.)

c. 1200, "not resembling," from un- (1) "not" + like (adj.). Similar formation in Old English ungelic, Old Frisian unlik, Old Norse ulikr, Middle Danish ulige, German ungleich.

unlike (adv.)

c. 1300, "unevenly," from un- (1) "not" + like (adv.) (see like (adj.)). From 1590s as "in a manner differing."