Nor

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Middle English: contraction of Old English nother ‘neither’.

wiktionary

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From Middle English nauther, from nother. Cognate with neither.

From Etymology 1 (sense 2 above), reinterpreted as not + or or negation + or

etymonline

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nor (conj.)

"and not," mid-13c., from ne (adv.) "no" + or (conj.), or else a contraction of Middle English nauther (see neither) and influenced in form by or. Generally correlative to neither or some other negative.