ἐμπεδορκέω
From LSJ
γραμματική ἐστιν ἐμπειρία τῶν παρὰ ποιηταῖς τε καὶ συγγραφεῦσιν ὡς ἐπὶ τὸ πολὺ λεγομένων → grammar is a practical knowledge of the usage of poets and writers of prose
English (LSJ)
A abide by one's oath, Hdt.4.201, X.Lac.15.7; ταῦτα IG22.111.79:—with a play on πέδη, Ar.Fr.772.
German (Pape)
[Seite 811] fest beim Eide bleiben, den Schwur halten, Her. 4, 201; Xen. Lac. 15, 7.