Lots of very plain-looking things work as trademarks. Some obvious examples: AAA, BBB, Target, Just Do It.
There's a lot of nuance in trademarks, including geographical nuance. It's possible for someone to open a small bakery in Boise, Idaho named Bread Stuff and not conflict at all with an existing local bakery named Bread Stuff that operates in Fresno, California.
Having different uses can count, too. Moe's Barber Shop can be a defensible trademark, but that doesn't necessarily conflict at all with Moe's Car Parts across town.
Except: There's also a concept of well-known trademarks, which supercede some of these things. There's a place called Gold and Silver Pawn Shop, in Vegas. There was a time person could build a pawn shop in Somewhere Else Entirely with that same name, and that'd be fine. But now that the Pawn Stars TV series has made the place very famous, it's something that would almost certainly be shown to be a well-known mark if someone were naive enough to try to use that name for their own new pawn shop, today. The Vegas shop would almost certainly win that court battle.
I'd like to think that notepad++ is also a well-known mark by this point.
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Anyway my intent earlier was just to help promote the concept of registration being optional-but-useful, not to write a book about trademarks. :)
And IANAL. I just got wrapped up in a trademark issue myself nearly 20 years ago, wherein I had been doing nothing wrong by using a name that another small company had been already been using in a very different market segment. Our uses were for very different things.
They subsequently got much bigger and arguably came to be well-known, and they wanted me to stop using that name. I had a valid case: I wasn't infringing when I started.
But I no money and no lawyers, while they had enough money and lawyers that there was no way I'd survive in court.
Hell, there was no way I'd even be able to afford to appear in court; I'd have lost by default and probably been required to pay for the whole mess. I was broke as fuck back then (I still am, but I was then, too).
But what I did have was some time, so I used that time to stuff my brain full of information about how trademarks work -- to prove to myself whether I had a leg to stand on as much as anything else.
I should have just given up. A sane person would have just washed their hands of it all and moved on. But I really liked the name I was using, and I am not always very sane.
It worked out OK, I guess: At the end of that very stressful time, I wound up giving them exactly what they wanted, and they ended up giving me some money in exchange. No courtroom was involved.
And now we're square. (And to be clear: I don't blame them at all for any of this. They're a good company. But even good companies are required to actively defend their trademark. Trademarks are not like patents: You need to use it, and actively defend it, or it is lost.)
