Snuffy's right on - Boudicca would probably not have considered herslf a "Celt" since that term didn't really exist until relatively recently, as applicable to Britons. She was queen of the Iceni, I believe, one of the many tribes of Britons inhabiting the isles when the Romans came. I doubt she would have been upset at being called a Briton, and would have been unlikely to know what you're talking about if you called her a Celt.