I am betting they are basing Frogadier off of Grenadier. Grendier is a french word, in would follow the same road as Greninja where they use a french word in his name.
Which would make it go more with the Ninja theme. Bu meaning grenade wielding soldier instead of military rank,
That pic is actually a fake its arms are not the same as the initial release. It was admitted to be fanart, that they then flipped and implemented into the game. There are to actual photos of Greninja that show 2 different movepools. Shows the new move water shuriken. and prove his legitimacy...
Okay I have been reading through this and I have decided to join in on the fun. You all do realize there are regional names for pokemon right. Greninja could easily just be the french name for the final evo for Froakie. Its quite possible when we buy the games on the twelfth and evolve are...