Lewis Short
(interjection) = εὖ: eu
* Well! well done! bravo! an exclamation of joy or approbation, Plaut. Most. 1, 4, 26; Ter. Phorm. 3, 1, 14; Plaut. Mil. 4, 4, 10; Ter. Eun. 1, 2, 74; Hor. A. P. 328.—Esp.: Eu Hercle!Plaut. Men. 5, 1, 31; id. Rud. 3, 5, 41; id. Most. 3, 1, 58 al. Cf. Hand, Turs. II. p. 609 sq.; and see euge.
Charlton T. Lewis, Charles Short, A Latin Dictionary