corpus n.

1610s, "of a material or physical nature, not mental or spiritual," with adjectival suffix -al (1) + Latin corporeus "of the nature of a body," from corpus "body" (living or dead), from PIE *kwrpes, from root *kwrep- "body, form, appearance." Meaning "relating to a material body or physical thing" is from 1660s. Related: Corporeality, corporeally.

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]

Proto-Indo-European root meaning "body, form, appearance," probably a verbal root meaning "to appear."

It forms all or part of: corporal (adj.) "of or belonging to the body;" corporate; corporation; corporeal; corps; corpse; corpulence; corpulent; corpus; corpuscle; corsage; corse; corset; incorporeal; incorporate; leprechaun; midriff.

It is the hypothetical source of/evidence for its existence is provided by: Sanskrit krp- "form, body;" Avestan kerefsh "form, body;" Latin corpus "body" (living or dead); Old English hrif "belly," Old High German href "womb, belly, abdomen."