LSJ
τά, (ὠνή) duty on goods sold, IG1². 329.5, Is. Fr. 43, PCair. Zen. 206.20, al. (iii BC), Poll. 7.15 ; also in sg., ἐπώνιον, τό, SIG 1014.5 (Erythrae, iii BC), etc.
something given into the bargain in a sale, Phryn. PS p. 70 B.
Liddell-Scott-Jones, Greek-English Lexicon (9th ed., 1940)