consummation (n.)

Middle English consummacioun, late 14c., "perfection;" c. 1400, "completion, accomplishment," from Latin consummationem (nominative consummatio) "a summing up; a finishing, a completing," noun of action from past-participle stem of consummare "to sum up, finish," from assimilated form of com "together, with" (see con-) + summa "sum, total," from summus "highest" (see sum (n.)). Sense of "completion of a marriage (by sexual intercourse)" is c. 1530.