"to kill (many beings) indiscriminately," commonly in reference to those who are not in a condition to defend themselves, 1580s, from Frenchmassacrer "to slaughter" (16c.), frommassacre (n.) "wholesale slaughter, carnage" (seemassacre (n.)). Sometimes 17c.-18c. merely "to murder cruelly," without reference to number. Related:Massacred;massacring.

"unnecessary, indiscriminate killing of human beings," sometimes also applied to wholesale slaughter of animals, 1580s, from Frenchmassacre "wholesale slaughter, carnage," from Old Frenchmacacre, macecle "slaughterhouse; butchery, slaughter," which is of unknown origin; perhaps related to Latinmacellum "provisions store, butcher shop," which probably is related tomactāre "to kill, slaughter."