A combination of the words "incredible" and "stoked."
The term was coined by "Paul" on the Duncan Trussell Family Hour podcast forums on May 14, 2012. It was first used to describe the feeling "Paul" experienced upon learning of Duncan's second podcast interview with the great and powerful Joey Diaz.
"Paul" questioned whether or not "incredistoked" was indeed a word. UrbanDictionary laid these fears to rest.
"Is Incredistoked a word? That's how I feel right now."