This phrase was made famous in Australia in the 1970's-80's. Over time it has come to mean a knock out punch.
The term was created to describe I blindside punch. Thrown from behind, it is usually a knock out punch not seen coming.
Media has misused the word as any K.O. or massive blow to the head.
-"Kimbo got knocked out!"
'What? How'd that happen?'
-"The bastard KING HIT 'Im."
'
Dog Act We'll fix him.'