absit omen (interj.)

"not present, not in a certain place" (of persons), "non-existent" (of things), late 14c., from Old French absent, ausent "absent" and directly from Latin absentem (nominative absens), present participle of abesse "be away from, be absent," from assimilated form of ab "off, away from" (see ab-) + esse "to be" (from PIE root *es- "to be"). Related: Absently; absentness.

"casual event or occurrence supposed to portend good or evil," 1580s, from Latin omen "foreboding, augury," according to Varro from Old Latin osmen; a word of unknown origin.