Apps I never installed appear in web store under "Other apps in my library"
I just had a look and found several apps that I'd never installed because they were pre-installed on one of my devices. I think that these may be apps that came with one device or another, but that you never noticed or made use of. In my 'other apps', I can see several pre-installed apps that I've disabled on my Acer Tablet. I suspect you're seeing the same thing, but that you paid even less attention to the pre-installed stuff than I did.