Derived from the Celtic element epo(s) "horse", combined with redo "to travel, to run" and rix "king." The name would thus mean "king of the running horses" - perhaps "king of the cavalry" is a little bit more appropriate. That is the usual explanation for the name. However, the name might also have been derived from Celtic eporeto "chariot" combined with rix "king", which would give the meaning "king of the chariot(s)." Either way, it is clear that the name is connected with horses and their speed.