LSJ
τά, asseverations on oath, Pl. Phdr. 241a. like ὅρκια, sacrifice on taking a solemn oath or swearing to a treaty, τὰ τῶν ὁ. καύματα Id. Criti. 120b, cf. OGI 229.82 (Smyrna, iii BC), IG 11(2).287 A 67 (sg., Delos, iii BC), SIG 1007.29 (sg., Pergam., ii BC). sg. ὁρκωμόσιον, τό, name of a place in Athens where a treaty or alliance had been sworn to, Plu. Thes. 27.
Liddell-Scott-Jones, Greek-English Lexicon (9th ed., 1940)