Infinite

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late Middle English: from Latin infinitus, from in- ‘not’ + finitus ‘finished, finite’ (see finite).

wiktionary

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From Middle English infinite, from Old French infinit and Latin infīnītus, from in-(“not”) + fīnis(“end”) + the perfect passive participle ending -itus.

etymonline

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infinite (adj.)

late 14c., "eternal, limitless," also "extremely great in number," from Old French infinit "endless, boundless" and directly from Latin infinitus "unbounded, unlimited, countless, numberless," from in- "not, opposite of" (see in- (1)) + finitus "defining, definite," from finis "end" (see finish (v.)). The noun meaning "that which is infinite" is from 1580s.