incisor (n.)
"cutting tooth," 1670s, from Medieval Latin incisor "a cutting tooth," literally "that which cuts into," from Latin incisus, past participle of incidere "to cut into, cut open, engrave," from in- "into, in, on, upon" (from PIE root *en "in") + -cidere, combining form of caedere "to cut" (from PIE root *kae-id- "to strike"). Inscisours as the name of a cutting tool is attested from early 15c. Related: Incisorial.