A bastardization of the phrase, "yeah, dude", used to express agreement or satisfaction.
It was most likely coined in the mid-1990's by teenage red-neck New Englanders, specifically those of Vermont.
The use of "yar tude" was mostly sarcastic and for comic relief, often by those of higher class who wished to imitate their lower class peers, and was often combined with buck which came to be known as a slang term for a "friend".
"Hey man, wanna get in my truck and go jack some deer?"
"Yar tude, buck. Let's get some beer and Marlboros first!"