When I was only homebrewing, I got a business license under the name "Dungeness Brewing. And a guy got on our clubs email list, using that name. I politely asked him to stop, as I had the license. He pointed out to me that he registered it as a DBA for a license he owned. So, I told him I would stop using the name, as he registered that before me.
Then he opens a nano-nano brewery, and called it something else entirely.
So, I resurrected my Dungeness Brewing name when I got my Brewer's Notice approved.
And of course he contacted me, and told (did not ask) for me to not use that name, as he registered it years before. (I had done my homework this time) I asked him to show me where he had used the name in the retailing of beer, and I would stop.
I haven't heard fro him since. What I learned it is actual USE of a name that offers protection (along with trademark and business license stuff. But no one can just register a name, not use it, and hold onto the rights.
(at least in my state)