From The Infinite Teen Slang Dictionary (thanks, peneli):
adv. used in conjunction with another word as an intensifier.
"That mobile phone is Joshua-enviable, Brian."
And then it gets weird.
"Hey, old chap, can you hook me up with some Josh?"
n. someone who flaunts homework.
"Buddy, check out that Desh's homework!"
So apparently we have "man, that Desh is an asshole about his Josh". What the hell?
Oh, and my last name's definition isn't printable.