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".