"a transgression or offense," in civil law, a misdemeanor, 1520s, from Latin delictum "fault, offense, crime," neuter singular of past participle of delinquere "to fail; be wanting, fall short; offend," from de- "completely" (see de-) + linquere "to leave" (from PIE root *leikw- "to leave"). Related: Delictable "criminal, wicked," early 15c. Phrase in flagrant delict translates Latin in flagrante delicto.
Delicts are commonly understood as slighter offenses which do not immediately affect the public peace, but which imply an obligation on the part of the offender to make an atonement to the public by suffering punishment, and also to make reparation for the injury committed The term delinquency has the same signification. [Century Dictionary]
1832, Latin, literally "body of the offense;" not "the murder victim's body," but the basic elements that make up a crime, which in the case of a murder includes the body of the victim. For first element, see corpus. With delictum "a fault, offense, crime, transgression," etymologically "a falling short" of the standard of law, neuter singular of past participle of delinquere "to fail; be wanting, fall short; offend" (see delinquent).
Thus, a man who is proved to have clandestinely buried a dead body, no matter how suspicious the circumstances, cannot thereby be convicted of murder, without proof of the corpus delicti--that is, the fact that death was feloniously produced by him. [Century Dictionary]