Lewis & Short

ăsĭnus, i, m. [acc. to Benfey, I. p. 123, and Hehn foll. by Curtius, an oriental word, perh. the Heb. [??], asina; cf. Goth. asilus; Lith. asilas; Erse, assul; Celt. asen or assen; Engl. ass; and Gr. ὄνος, which latter two forms the Lat. seems to have in combination], an ass.

  1. I. Lit., Cato, R. R. 10, 1; 11, 1; Varr. R. R. 2, 1, 14; 2, 6, 1 al.; Col. 6, 37, 8; 6, 7, 1 al.; Plin. 8, 43, 68, § 167 sqq. et saep.; Vulg. Gen. 12, 6; ib. Isa. 1, 3; ib. Luc. 13, 15; 14, 5 et persaepe.
    Prov.: qui asinum non potest, stratum caedit, i. e. he, that cannot find the offender, avenges himself on the unoffending, Petr. 45, 8: in tegulis, of an odd appearance, id. 45, 63: ad lyram, of an awkward man, acc. to Varr. ap. Gell. 3, 16: sepulturā asini sepelietur, of a contemptible and unworthy man, Vulg. Jer. 22, 19.
  2. II. Trop., an ass, a dolt, simpleton, blockhead: neque ego homines magis asinos umquam vidi, Plaut. Ps. 1, 2, 4; Ter. Heaut. 5, 1, 4.
    Hence, as a term of insult: Quid tu autem huic, asine, auscultas? Ter. Ad. 5, 8, 12; id. Eun. 3, 5, 50: Quid nunc te, asine, litteras doceam? Non opus est verbis, sed fustibus, Cic. Pis. 30.