c. 1300, "charge (with an offense, fault, error, etc.), impugn, blame," from Old French acuser "to accuse, indict, reproach, blame" (13c., Modern French accuser), earlier "announce, report, disclose" (12c.), or directly from Latin accusare "to call to account, make complaint against, reproach, blame; bring to trial, prosecute, arraign indict," from ad causa, from ad "with regard to" (see ad-) + causa "a cause; a lawsuit" (see cause (n.)). "Accuse commonly, though not invariably, expresses something more formal and grave than charge" [Century Dictionary, 1902]. Related: Accused; accusing; accusingly.
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Harper, D. (n.d.). Etymology of Accused. Online Etymology Dictionary. Retrieved $(datetime), from https://www.etymonline.com/word/Accused