Group A runes were most common in Viking Age Denmark
Grein
Old Norse Grein (m.)
Grein is an original byname of which the interpretation is not certain. It is derived from Old Norse grein ‘branch’ or ‘reason’ or ‘distinction’ or ‘discernment’.
There are some few late instances of the name recorded in West Scandinavia. It is also the first element in Grainsby, Lincolnshire.