Old Testament prophet whose name has four vowels (6)
![Ross](/clue/static/ross-mug.min.png)
I believe the answer is:
isaiah
(Other definitions for isaiah that I've seen before include "Book of prophecies in the Bible" , "A philosophical Berlin" , "8th century BC Hebrew prophet" , "Sir - Berlin, twentieth century political historian" , "Biblical Book of Prophecies" .)