Of uncertain origin. Two possibilities are: * From Old Latin *augos (“reinforcement, increase”) (genitive *augeris), related to augeō (“to increase”), from Proto-Indo-European *h₂éwgos; compare Sanskrit ओजस् (ojas, “strength, vigor”), Avestan 𐬀𐬊𐬘𐬀𐬵 (aojah), 𐬀𐬊𐬔𐬀𐬵 (aogah, “might, power”) as well as Latin augustus (< *h₂éwgos-tos). The noun *augos would have developed from "reinforcement" to "(one) who makes grow". This derivation is preferred by De Vaan. * From avis (“bird”) + garrire (“to talk”), as augurs were known to observe the behavior of birds.