The eight-letters thing becomes relevant, then. I can't think of an 8-letter generic horse word, can you?

I just don't know enough about Napoleonic history to tell! Hence the flist appeal. It's probably a last name, and must be someone remembered by history if he's taunting his readers with a riddle. I considered Arthur Wellesley before reading the 'didn't appear in the books' bit, because Sharpe has a serious man crush on him, AFAIK.