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.
"to chat," 1828, of uncertain origin; perhaps from French causer "to talk," from Latin causari "to plead, dispute, discuss a question," from causa (see cause (n.)).
1530s, in grammar and logic, "expressing a cause," from Latin causalis "relating to a cause," from causa "a cause, reason" (see cause (n.)). From 1560s as "relating to a cause or causes;" 1640s as "being a cause, producing effects."
early 15c., "effective as a cause or agent," from Old French causatif, from Latin causativus, from causa "a cause, reason" (see cause (n.)). Meaning "expressing causation" is from c. 1600; hence the noun, in grammar, "a form of a noun or verb expressing causation" (1824).
late 14c., "charge of wrongdoing," from Old French acusacion "charge, indictment" (Modern French accusation) or directly from Latin accusationem (nominative accusatio) "formal complaint, indictment," noun of action from past-participle stem of accusare "call to account, make complaint against," from ad causa, from ad "with regard to" (see ad-) + causa "a cause; a lawsuit" (see cause (n.)). Meaning "that which is charged (against someone)" is from early 15c.
late 14c., recusen, "to decline, refuse," especially "reject another's authority or jurisdiction over oneself as prejudiced," from Old French recuser (13c.) and directly from Latin recusare "make an objection against; decline, refuse, reject; be reluctant to," from re- (see re-) + causa (see cause (n.)). Specifically, in law, "reject or challenge (a judge or juror) as disqualified to act." The word now is used mostly reflectively. Related: Recused; recusing; recisative.