1690s, "serving to distinguish," especially of a mark or sign added to a letter to distinguish it from another of similar form or indicate a peculiar accent, tone, or stress, from Latinized form of Greek diakritikos "that separates or distinguishes," from diakrinein "to separate one from another," from dia "between" (see dia-) + krinein "to separate, decide, judge" (from PIE root *krei- "to sieve," thus "discriminate, distinguish"). As a noun, "a diacritical mark," from 1866. Related: Diacritical.
