early 15c., "action of alleging, formal declaration in court," from Old French alegacion "allegation, affirmation" (Modern French allégation) and directly from Latin allegationem (nominative allegatio) "a sending, dispatching," noun of action from past-participle stem of allegare (see allege). Specifically in law, "assertion of a party to a suit or action, which he intends to prove." In general (non-legal) use, since 17c., often suggesting an assertion without proof.