A lot of the "Mystery names" on the list sounds an awful lot like made-up Swedish towns (I'm assuming that if they were real the author would have found them). E.g.:

Bergsbo - could be a made-up town name, but it could also roughly be translated to "mountain dweller".

Bertby - Would literally translate to Bert (Swedish boy's name) village.

Biby - Bee village.

Billsta - -sta is a common suffix for places in Sweden.

Bjurön - Bjur is an old name for beaver, and the name literally translates to Beaver Island. Furthermore, bjur is (according to the Swedish National Encyclopedia) a common prefix used in village names. https://www.ne.se/uppslagsverk/encyklopedi/l%C3%A5ng/bjur.