(Ἰωνίδες or Ἰωνιάδες), a name borne by four nymphs believed to possess healing powers. They had a temple on the river Cytherus in Elis, and derived their name from a mythical Ion, a son of Gargettus, who was believed to have led a colony from Athens to those districts. The story undoubtedly arose from the existence of a mineral spring on the spot where their sanctuary stood. (Paus. 6.22.4; Strab. viii. p.356.)
[L.S]A Dictionary of Greek and Roman biography and mythology
Smith, William
A Dictionary of Greek and Roman biography and mythology. William Smith, LLD, ed. 1890