"resembling or pertaining to birds," 1861, from Latin avis "bird" (from PIE root *awi- "bird") + -an.
Entries linking to avian
*awi-
Proto-Indo-European root meaning "bird." It also might be the source of *woyo, *oyyo, Proto-Indo-European words for "egg."
It forms all or part of: auspex; auspices; auspicious; avian; aviary; aviation; aviator; avicide; aviculture; aviform; caviar; cockney; egg (n.); ocarina; oo-; oocyte; oolite; oology; osprey; ostrich; oval; ovary; ovate (adj.); oviform; oviparous; ovoviviparous; ovoid; ovulate; ovulation; ovule; ovum.
It is the hypothetical source of/evidence for its existence is provided by: Sanskrit vih, Avestan vish, Latin avis "bird;" Greek aietos "eagle;" Old Church Slavonic aja, Russian jajco, Breton ui, Welsh wy, Greek ōon, Latin ovum, Old Norse egg, Old High German ei, Gothic ada all meaning "egg."
-an
word-forming element meaning "pertaining to," from Latin -anus, adjective suffix, in some cases via French -ain, -en. From PIE *-no-.