Labour

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Middle English: from Old French labour (noun), labourer (verb), both from Latin labor ‘toil, trouble’.

wiktionary

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From Middle English labouren, from Old French laborer, from Latin laborare(“(intransitive) to labor, strive, exert oneself, suffer, be in distress, (transitive) to work out, elaborate”), from labor(“labor, toil, work, exertion”); perhaps remotely akin to robur(“strength”). Displaced native English swink(“toil, labor”).

etymonline

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labour

chiefly British English spelling of labor (q.v.); for spelling, see -or. With capital L-, short for "the British Labour Party," it is attested from 1892; the party name itself is from 1886.