Lewis & Short

fīdo, fīsus sum (ante-class. form of the fut. fidebo, Nov. ap. Non. 509, 4), 3, v. n. [root in Sanscr. bandh, unite; Gr. πείθω, persuade, πεῖσμα, cable; Lat. fidus, Deus Fidius, foedus; cf.: fascis, fascia; Curt. Gr. Etym. p. 262; but Fick refers fido to root bhidh; Goth. beidan; Engl. bide, to expect; Vergl. Wört. p. 380], to trust, confide, put confidence in, rely upon a person or thing (rare; in the verb. finit. mostly poet.; but class. in the part. praes. and P. a.).

        1. (α) With dat.: fidere nocti, Verg. A. 9, 378: fugae fidens, id. ib. 11, 351: pestilentiae fidens (with societate fretus), Liv. 8, 22, 7: taedae non bene fisa, Ov. M. 15, 827: qui sibi fidit, Hor. Ep. 1, 19, 22; id. S. 2, 2, 108: puer bene sibi fidens, Cic. Att. 6, 6, 4.
        2. (β) With abl.: hac (Cynosurā) fidunt duce nocturnā Phoenices in alto, Cic. poët. N. D. 2, 41, 106; id. Ac. 2, 20, 66: arcu fisi Getae, Ov. P. 4, 9, 78: cursu, id. M. 7, 545: ope equinā, id. ib. 9, 125: pecuniā, Nep. Lys. 3 fin.: prudentiā consilioque fidens, Cic. Off. 1, 23, 81.
          Doubtful, whether dat. or abl. (v. Zumpt, Gr. § 413; cf. confido): nec nitido fidit adultero, Hor. C. 3, 24, 20: pictis puppibus, id. ib. 1, 14, 15: (Jugurtham) Mario parum fidere, Sall. J. 112, 2: ingenio, Quint. 10, 7, 18; cf.: ingenio suo, Plin. Ep. 4, 13 fin.: suis rebus, Cic. Att. 10, 8, 2.
        3. (γ) With inf.: fidis enim manare poëtica mella Te solum, Hor. Ep. 1, 19, 44; Sil. 1, 432: parum fidens pedibus contingere matrem, Luc. 4, 615: fisus cuncta sibi cessura pericula, Caesar, id. 5, 577.
        4. (δ) Absol.: ubi fidentem fraudaveris, i. e. who trusts (you), Plaut. As. 3, 2, 15.
          Hence, fīdens, entis, P.a. (lit., trusting to one’s self, self-confident; hence), confident, courageous, bold: qui fortis est, idem est fidens, qui autem est fidens, is profecto non extimescit: discrepat enim a timendo confidere, Cic. Tusc. 3, 7, 14: fidenti animo gradietur ad mortem, id. ib. 1, 46, 110; cf.: tum Calchas haec est fidenti voce locutus, id. poët. Div. 2, 30, 64: fidens animi, Verg. A. 2, 61; Tac. A. 4, 59 fin.; so, fidens armorum, Luc. 9, 373.
          Comp.: Romanus, fidentior, Amm. 16, 12 al.
          Sup.: fidentissimo impetu acies motae, Amm. 27, 10, 12.
          Adv.: fīdenter, confidently, fearlessly, boldly: timide fortasse signifer evellebat, quod fidenter infixerat, Cic. Div. 2, 31, 67: agere, id. Ac. 2, 8, 24: confirmare, id. de Or. 1, 56, 240; cf. id. N. D. 1, 8, 18.
          Comp.: paulo vellem fidentius te illi respondisse, Cic. Att. 6, 1, 21.
          Sup.: accedere fidentissime, Amm. 17, 1, 9; August. Ver. Rel. 3.