1540s, from Latin augur, a religious official in ancient Rome who foretold events by interpreting omens, perhaps originally meaning "an increase in crops enacted in ritual," in which case it probably is from Old Latin *augos (genitive *augeris) "increase," and is related to augere "increase" (see augment). The more popular theory is that it is from Latin avis "bird," because the flights, singing, and feeding of birds, along with entrails from bird sacrifices, were important objects of divination (cf. auspicious). In that case, the second element would be from garrire "to talk."
c.1600, from augur (n.). Related: Augured; auguring.