Coupling

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Middle English: from Old French cople (noun), copler (verb), from Latin copula (noun), copulare (verb), from co- ‘together’ + apere ‘fasten’. Compare with copula and copulate.

wiktionary

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From Middle English couplyng; equivalent to couple +‎ -ing.

etymonline

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coupling (n.)

mid-14c., "the joining of one thing to another," verbal noun from couple (v.). From late 14c. as "the joining of two persons in love or marriage," also "copulation." Meaning "that which couples or connects" is from 1540s.