late 14c., copulacioun, "a coupling, joining, uniting," from Latin copulationem (nominative copulatio) "a coupling, joining, connecting," noun of action from past-participle stem of copulare "join together, couple, bind, link, unite," from copula "band, tie, link" (see copulate). Specific sense of "sexual intercourse, coition" is from late 15c., and this became the main sense from 16c.
