ἀντόμνυμι
From LSJ
τραχὺς ἐντεῦθεν μελάμπυγός τε τοῖς ἐχθροῖς ἅπασιν → he is a tough black-arse towards his enemies, he is a veritable Heracles towards his enemies
English (LSJ)
A swear in turn, swear on the other part, in a treaty, c. fut. inf., X.HG3.4.6, Ages.1.10. II as Att. law-term, make an affidavit, both of the accuser and the defendant (cf. ἀντωμοσία), Antipho 1.18, Is.9.1, D.43.3, etc.:—in Med., Is.5.16.
German (Pape)
[Seite 264] (ὄμνυμι), dagegen schwören, ἀντομωμοκώς Antiph. 1, 8; ἀντώμοσαν Xen. Hell. 3, 4, 6; Is. 5. 1; ἀντομόσαι Dem. 43, 3. Vgl. ἀντωμοσία.