To beat: originally confined to beating with the hilt of a sword, the knob being, from its similarity to a small apple, called pomelle; in Spanish it is still called the apple of the sword. As the clenched fist likewise somewhat resembles an apple, perhaps that might occasion the term pommelling to be applied to fisty-cuffs.
POMMEL
Meaning of POMMEL in English
Slang English vocab. Английский сленговый словарь. 2012