c. 1200, "reason or motive for a decision, grounds for action; motive," from Old French cause "cause, reason; lawsuit, case in law" (12c.), and directly from Latin causa "a cause; a reason; interest; judicial process, lawsuit," which is of unknown origin.
From mid-14c. as "cause of an effect; source, origin." From late 14c. as "that which affords opportunity for a cause to operate, occasion;" also "reason for something taking place or for something being so; rational explanation." Also late 14c. as "proper or adequate reason, justification for an action." Sense of "matter of interest or concern; a side taken in controversy" is from c. 1300. Cause célèbre "celebrated legal case" is 1763, from French. Common cause "a shared object or aim" is by 1620s.
late 14c., "produce an effect," also "impel, compel," from Old French causer "to cause" (13c.) and directly from Medieval Latin causare, from Latin causa "a cause; a reason; interest; judicial process, lawsuit," which is of unknown origin. Related: Caused; causing. Classical Latin causari meant "to plead, to debate a question."