[mrweasel]

I think it's just taking the lists of approved/used names in each country. Denmark has a ton of technically approved names, to accommodate refugees and immigrants, but they don't work well in Danish, because they are Arabic, Somali or whatever in origin.

Perhaps easier to understand examples are Kathy and Abigail. Pretty names in English but they will get completely butchered in Danish. Kathy will pretty much lose the h, and become Cat-i. Abi works, but gail will sound like the German "geil".