astus.

Of uncertain origin. Suggestions include: * from Proto-Indo-European *h₂éd-*sth₂u- (“a standing by”), from *steh₂-, thus formed to astō (“to stand by”) like the verb praestō to the adverb of the same form, with a by-form praestū. In this case the full nominal declension is secondary; * from Ancient Greek ἄστυ (ástu), from the common characterization of city-dwellers as more intelligent, also seen in urbānus; however, in the latter this appears to be a Late Republican development. * from Proto-Indo-European *h₂eḱst-, Proto-Indo-European *h₂eḱ- (“sharp”) - compare Lithuanian aksti̇̀s, Latvian aksts (“prickle, sharp point”), Proto-Celtic *akstīno- (“furze, gorse”). In this case, the Proto-Italic form would be *akstus. A long vowel is once attested for ā̆stūtia, which would be unexpected but paralleled by ācer. Attested since Plautus (second half of the 3d century BCE).