"one who observes flights of birds for the purpose of taking omens," 1590s, from Latin auspex "interpreter of omens given by birds," from PIE *awi-spek- "observer of birds," from root *awi- "bird" + root *spek- "to observe." Compare Greek oionos "bird of prey," also "bird of omen, omen," and ornis "bird," which also could mean "omen."
