After reading the captions and explanations concerning the use of the name Cocidius, I feel pretty much confirmed in my personal views about the meaning of interpretatio Romana vel Graeca. The name of a specific Roman god like Mars or Iuppiter are added to specify the aspect under which the specific numen is to be invoced.

There seem to be similarities to the cult of Epona among Batavians the Germania inferior. Epona is a Celtic goddess, and the cult was adopted by the Batavi and adapted as the specific goddess to protect the horses and riders from harm (other than in battle?).

Even today, people adopt foreign or "outdated" cults and evolve them to create new cults and rites adapted to their own ways of life and thinking. It seems to be very human - but it was suppressed by Christian thought, especially after the end of the Middle Ages.

At least, the name does not sound Germanic to me. What do our friends at Cilipeid Celtica - Gaul say? Vortigern - the ball is yours!