Odour

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Middle English: from Anglo-Norman French, from Latin odor ‘smell, scent’.

wiktionary

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From Middle English odour, borrowed from Anglo-Norman odour, from Old French odor, from Latin odor. Related to Swedish odör(“bad smell”).

etymonline

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odour (n.)

chiefly British English spelling of odor (q.v.); for spelling, see -or.