From the first post from Serack: "So I'm now home from the Washington DC signing, and I got to ask Jim if there was significance to his choice of Fitz's name. First he confirmed that he was aware Fitz means bastard, and he softly confirmed that this was intentional, and we would see how eventually"
I know there is another WoJ about Fitz as a single book character, but I don't have the exact words.