hit
to strike
mon
monster
top
spinning top on which it’s based
http://pokemondb.net/pokedex/hitmontop
Origin: Hitmontop is based on a top and a practitioner of capoeira.
Name origin: Hitmontop is a combination of hit, monster, and top (a
reference to spinning tops and how it fights, by spinning on its
head), perhaps meaning "hit 'em on top". The name is also related to
Hitmonlee and Hitmonchan, both of which are parallel evolutions to it
as of Generation II. Kapoerer is derived from capoeira, a Brazilian
martial art that often involves spinning one's legs in the air.
http://bulbapedia.bulbagarden.net/wiki/Hitmontop#Origin