1610s, "not to know, to be ignorant of," from French ignorer "be unaware of" (14c.), or directly from Latin ignorare "not to know, be unacquainted; take no notice of, disregard" (see ignorant). The original sense in English is obsolete. Sense of "pass over without notice, pay no attention to" in English first recorded 1801 (Barnhart says "probably a dictionary word"), and OED indicates it was uncommon before c. 1850. Related: Ignored; ignoring.