c.1400, "physical, human, mortal," from Old French carnal and directly from Medieval Latin carnalis "natural, of the same blood," from Latin carnis "of the flesh," genitive of caro "flesh, meat" (see carnage). Meaning "sensual" is from early 15c.; that of "worldly, sinful" is from mid-15c. Carnal knowledge is attested from early 15c. and was in legal use by 1680s.