ethic (n.)

late 14c., ethik "study of morals," from Old French etique "ethics, moral philosophy" (13c.), from Late Latin ethica, from Greek ēthike philosophia "moral philosophy," fem. of ēthikos "ethical, pertaining to character," from ēthos "moral character," related to ēthos "custom" (see ethos). Meaning "moral principles of a person or group" is attested from 1650s.