dattebayo the word that naruto often ends his sentances with. verbaly, it is said as "-ttebayo"
dattebayo has no real meaning, and the closest english equivelent is a pirates "arrgh!"
in the english dub (which is constantly plauged by crazed otaku, despite it being an excelent dub and true to the original)it is translated as "belive it!" in order for the mouth flaps to fit.
The specific "dattebayo" is not well known to even much of the Japanese native population.
The "dattebayo" specific ending can be considered a colloquial verb ending that makes the speaker sound uncultured, brusque, and trying to seem tougher than they really are.