That's because you're doing something that directly competes with an existing trademarked product. Windows is a computer operating system, so of course you can't make another computer operating system and call it "Windows".
However, if you want to make some breakfast cereal called "Windows bran flakes", you're absolutely allowed to do that under trademark law, because it has zero to do with computer operating systems. Just make sure the box doesn't look like Windows 10, or the Microsoft/Windows logos, or anything like that.
What we're seeing here is total overreach. "Backcountry" is a common word that's been around for centuries. So yeah, it would certainly be wrong for someone to start an online retail business selling outdoor stuff and call it "backcountry-equipper.com" or something like that. But they're suing people who are doing totally different stuff, like making jeans, not people operating online retailers of various outdoor equipment.
The point could be that window in Windows means an area of the screen dedicated for an application to display output and receive input from the user, and such meaning is generic for operating systems.
However, if you want to make some breakfast cereal called "Windows bran flakes", you're absolutely allowed to do that under trademark law, because it has zero to do with computer operating systems. Just make sure the box doesn't look like Windows 10, or the Microsoft/Windows logos, or anything like that.
What we're seeing here is total overreach. "Backcountry" is a common word that's been around for centuries. So yeah, it would certainly be wrong for someone to start an online retail business selling outdoor stuff and call it "backcountry-equipper.com" or something like that. But they're suing people who are doing totally different stuff, like making jeans, not people operating online retailers of various outdoor equipment.