Board Thread:General Discussion/@comment-26281589-20130831200528/@comment-16502426-20130912000213

Jaune is pronounced in French almost exactly the same as they are pronouncing it in the show, just with a difference in accent.

Joan is a completely different word, and (if I'm not mistaken) is feminine.

So to deal with this, they take Joan of Ark, and replace Joan with a similar looking and somewhat similar sounding word that means "yellow", and also sounds like the masculin name "john" and its relatives. Thus we end up with Jaune Arc.