corporal (n.) Look up corporal at
lowest noncommissioned army officer, 1570s, from Middle French corporal, from Italian caporale "a corporal," from capo "chief, head," from Latin caput "head" (see capitulum). So called because he was in charge of a body of troops. Perhaps influenced by Italian corpo, from Latin corps "body." Or corps may be the source and caput the influence, as the OED suggests.
corporal (adj.) Look up corporal at
"of or belonging to the body," late 14c., from Old French corporal (12c., Modern French corporel) "of the body, physical, strong," from Latin corporalis "pertaining to the body," from corpus (genitive corporis) "body" (see corporeal). Corporal punishment "punishment of the body" (as opposed to fine or loss of rank or privilege) is from 1580s. Related: Corporality.