Origins of surname TROR(E)Y

This surname is very rare in the UK, there appear to be none in Australia and a handful in Canada & USA. Any TRORYs found in British records generally fit into one of just four Trees which so far go back to 1700s. The few TRORYs in N. America fit into these Trees as well. All of these Trees go back to Norwich in the county of Norfolk (eastern coastal region of England) circa mid 1700s. Church Records in England show the name in 1500s as being TRORA, THRORA, THRORY. I am of the opinion that there is an old connection to Norway and only recently a Norwegian ship's captain remarked "That sounds Norwegian". I have read up what I can and THORIR comes to mind. TROR(E)Y is not English. It doesn't appear in the Oxford University Press Dictionary of English Surnames which is a highly respected and very thorough book. Any comments gratefully received or perhaps somebody knows an academic person who may know??? Thank you.