Origin of Grung family in Bergen

My grandmother, Jenny Marie Grung was born in Bergen in 1856. I have been able to trace her line back to Frantz/Frans Diderich/Didrich Grung, born about 1701, using the National Archives. I cannot find information for his birth. He married Giertke Hansdatter Bildoe, a local girl, in 1724 in Bergen. They had 9 children in Bergen and for all baptisms Frantz is recorded as a Grung. His descendants (mostly in Bergen) make up the majority of Grungs in the database. However in the record of his death at age 43 in 1744 he is down as a Grundt. I have checked digital copies of the original records and the spelling is as recorded. My question is where could he have come from and how do I find out? I have thought of 2 possibilities. Could he have come from Grong in Sor-Trondelag? At the time he probably came to Bergen (early 1700s), according to Rygh's farm names, Grong could have been spelled as Grung. His first names are not very typical and with the spelling Grundt on his death notice, could he be a German/Prussian/Dane immigrant? Any suggestions/help, please!