assault, hit, beat, thrash
殴 centers on striking someone or something with force: assaulting, hitting, beating, or thrashing.
殴 combines 区 (possibly phonetic) with 殳 (a hand holding a weapon or tool), suggesting striking or hitting. The exact historical development is uncertain.
The left side 区 looks like a boxed area, and the right side 殳 resembles a hand holding a stick. Imagine someone trapped in a box being beaten with a stick: 殴 means assault or hit.
For オウ, imagine the sound of a punch landing: 'Ow!' That 'Ow' cues オウ, and it fits the meaning of hitting.
to strike; to hit; to beat; to punch
fist fight
hit; strike; blow
to hit hard; to punch hard; to give a hard blow; to wallop; to sock
raid; attack; assault
striking on the side; side blow
to hit hard; to strike hard
hitting endlessly; beating up comprehensively
to hit with a club
to throw a punch at; to swing at; to strike out at; to raise a hand against
to raid; to storm; to launch an attack (on); to mount an assault (on)
to knock down; to knock out
to exchange blows; to hit each other; to punch each other; to fight
scribble; scrawl
to strike dead; to beat to death
to knock (a person) off his feet; to hit (something) hard; to send (someone) flying
punching and kicking
beating to death; striking dead