This is "Look up" functionality on MacOS. Recently it's added "Siri Knowledge" and "Book Store" to it's look up options.
My MacOS' language is set to English. I only read English-language ebooks from Apple's book store. My phone has alway been set to English. And you can clearly see that Apple's book store fully respects that. The category is "poesi", and language is "engelska". Because when your location is Sweden, how can you ever want any other language but Swedish?
Why not Czech or Hungarian, one wonders: grumpy.website/post/0RmkKSxH6