WHAT WE KNOW: Mr. Gunshock said his name was Doctor Diagnosan. The Journey Logs say his name is "Diagnosan Tocot". (note: The Journey Logs have been known to be wrong before)
WHAT I SPECULATE: Dr. Diagnosan is a really cheesy name for a miracle doctor. Even worse than naming a planet full o' lawyers Litigara. Therefore, I think Dr. D. is a Doctor who is like those car salesmen you see on the local commercials. Dr. Diagnosan is the Uncharted Territories version of "Happy Harry," "Happy Doctor Diagnosan Tocot."