That's a nice thing to play with!

I do wonder though if the original search on 'napoleon' might have included some of the *other* Napoleon?

If you search on 'Napoleon Bonaparte' you get a quite different result:

http://ngrams.googlelabs.com/graph?content=Napoleon+Bonaparte&year_start=1800&year_end=2000&corpus=0&smoothing=3

Emperor Napoleon:

http://ngrams.googlelabs.com/graph?content=Emperor+Napoleon+&year_start=1800&year_end=2000&corpus=0&smoothing=3

This is fun