Perhaps you accidentally imported something that uses those genre tags. Based on the values you listed, maybe a newspaper or newspaper article? Or book?
I also get a bunch of new/different genres when I download Cloudplay tracks since I have my own very specific way I categorize and name genres. If you recently downloaded something from Cloudplay, it might have included tracks/data that used those genre tags.
Thanks, that was my guess too but does not seem to explain what I see:
1) When I edit Genre for media types Audio, Video, Document I am presented with only choices I have previously used. When I edit Genre for media type Image I am presented with extra choices I have never used.
2) The extra choices are oddly separated from the genres I have previously used. They are randomly sorted as a group that precedes the alphabetically sorted group of genres I have previously used.
3) I double checked that no imported images use the extra genres. I suppose it's possible that some images I imported may have had those genres initially but I have definitely change the genre to one of my standard choices.
I'm wondering if this has something to do with the recent changes to EXIF support?