convict (n.)

late 15c., "person proved or found guilty of an alleged offence," from obsolete adjective convict "convicted," from Latin convictus (see convict (v.)). Slang shortening con is from 1893.

convict (v.)

mid-14c., "to convince by arguments, convince of wrongdoing or sin" (a sense now obsolete), from Latin convictus, past participle of convincere "to 'overcome' in argument, to overcome decisively; to convict of crime or error," from assimilated form of com-, here probably an intensive prefix (see com-), + vincere "to conquer" (from nasalized form of PIE root *weik- (3) "to fight, conquer").

Meaning "prove or find guilty of an offense charged" is from late 14c. It replaced Old English verb oferstælan. Related: Convicted; convicting.