köken: Perhaps from the base *aut, imitative of its call, + -illo. Or, from Vulgar Latin *ōtellus, a diminutive of Ancient Greek ὠτός (ōtós), genitive of οὖς (oûs, “ear”), referring to its ears.
köken: From an imitative reduplicated root, perhaps ultimately Proto-Indo-European *(H)ulu(l)- (“to cry out, howl; owl”). Compare Sanskrit उलूक (ulūka, “owl”), sometimes also compared to Hittite 𒄷𒉿𒆷𒀸 (ḫu-wa-la-aš, “a kind of bird: owl?”) and Proto-Germanic *uwwalǭ (“owl”), though these may all be independent onomatopoeias. More at ululō (“howl, screech”). Compare also upupa.