LSJ
Att. ἐπιθαρρέω, put trust in or on, θεῶν ἀρωγαῖς Plu. Brut. 37, cf. S.E. M. 1.270.
take heart to resist, τοῖς ἐχθροῖς App. BC 3.10, cf. Ael. NA 4.34, 9.1; ἐ. τῷ πελάγει venture on…, ib. 5.56; abs., take courage, D.C. 41.50, al.
Liddell-Scott-Jones, Greek-English Lexicon (9th ed., 1940)