In addition to my previous information I would add that the Gjestvang name is found both in Hedmark and Oppland counties, which are divided by Lake Mjøsa. In fact the name probably originates from Oppland, probably around the town of Gjøvik.
There was an Olympic speed skater of the name Alv Gjestvang, who participated I believe in the 1960 and 1964 Winter Olympics.