FIDIUS

An ancient form of filius, occurs in the connection of Dius Fidius, or Medius fidius, that is, me Dius (Dios) filius, or the son of Jupiter, that is, Hercules. Hence the expression medius fidius is equivalent to me Hercules, scil. juvet. (Cic. ad Fam. v. 21; Plin. Epist. iv. 3.) Sometimes Fidius is used alone in the sense of the son of Jupiter, or Hercules. (Ov. Fast. vi. 213; comp. Varro, de L. L. v. 66; Plaut. Asin. i. 1. 8; Varro, ap. Non. viii. 93.) Some of the ancients connected fidius with fides. (Festus s. v. medius.)