Epona

Ĕpŏna, ae, f. [from equus; cf. Gr. ἵππος; but referred to root ap- of apo by Fick, Wörterb. p. 425],

the protecting goddess of horses , asses , etc., Tert. ad Nat. 1, 11; id. Apol. 16; Juv. 8, 157; Prud. Apoth. 197; Ap. Met. 3, 27, 7; Inscr. Orell. 402; 1792 sq.