An Etymological Dictionary of the German Language/Schnapphahn
Schnapphahn, m., ‘highwayman,’ from the equiv. late MidHG. snaphan; yet it seems that the word signified orig. a sort of musket, although this meaning is first recorded at the end of the 17th cent., and hence is later than ‘mounted highwayman,’ which occurs even in the 15th cent.; the signification ‘musket’ was afterwards transferred to the man armed with such a weapon. Comp. Du. snaphaan, ‘gun, musket, bandit.’