Seriously I've never heard anyone on the justice league or anyone call him "Martian Manhunter" it's always "J'onn"

I may never know

Dunno. Some heroes are normally called by name and some are called by their hero names

He calls himself Martian Manhunter.

@willpayton: When?

@giantsfan576: Manhunter is a title her earned while on Mars, basically a police-man.

0:56

They barely refer to him as MM completely... I do recall Supes, Bats and Diana referring to him as "Martian" on rare occasions but that's it.

They do in Jl:Doom

ive heard it a couple of times. cant say where though.

Its been done a couple of times. Last I remeber Steve did it in either JLA #1 or 2.