He will be known as HRH Prince George of Cambridge, and when he becomes King, probably either King George VII or King George VIII. (There is some speculation as to whether HRH Charles, the Prince of Wales will take either one of the regnal names: King Charles III or King George VII. Charles, the Prince of Wales, has responded by stating that he hasn't picked a regnal name. However, his name is Charles Philip Arthur George.)
I'm not surprised that this would be a name for the son of HRH Prince William, the Duke of Cambridge, as King George V and King George VI are well-liked monarchs. On the flip side, I would expect any daughters of HRH Prince William, the Duke of Cambridge to have Elizabeth or Victoria as one of their names.
I don't care what they name their child.
"And I don't know why Louis should be so special to William."
Yeah, I don't know why Louis is so special to William Arthur Philip Louis.