Kill/do in

Thanks again for the prison/jail discussion. It sparked another discussion here as to the many different synonymns and origins of to kill.
to do in
to off someone
to whack
to smoke
assassinate
murder
peel their cap
split their wig

Maybe ESC can shine some light on "to do someone in."

Not much light.

Merriam-Webster:
Main Entry: do in
Function: transitive verb
1 a : to bring about the defeat or destruction of; also : KILL b : EXHAUST, WEAR OUT
2 : CHEAT

Do in - verb to kill. 1905 "I heard people tell her to do me an injury, throw glasses at me, and 'do me in.'" From Random House Historical Dictionary of American Slang, Volume 1, A-G by J.E. Lighter, Random House, New York, 1994.