Threads Software Limited says its lawyers have informed Meta that it will seek an injunction from the courts if the Facebook parent keeps using the name Threads...
Meta given 30 days to cease using the name Threads by company that trademarked it 11 years ago::undefined
There's colloquial use, what you're talking about, and then there's the actual branding on the product and the marketing. Only the company with the trademark can use the trademarked work on the product and in their marketing.
You can't copyright a word. You can't patent a word. But you can trademark a word. Trademarking a word gives you the exclusive right to use that word to identify your products but only within the specific market it is registered in.
A few more examples of trade marked words, apple, meta, cherry, target, zoom.
Are any of those trade names invalid simply because they are preexisting words? No. That's trademark law.
Meta will disclaim the word Threads because it is too generic. So you can trademark whatever you want, but when someone comes along and wants to use it, if you've trademarked something generic, like Threads, then you go to court and presumably have them rule whether or not you can use it. And that probably will happen.
According to Trademark law in many places you can.
Generally, you can only enforce your trademark (successfully) if the infringing group is in the same industry. So if I sold an educational service or toilet bowl cleaner called Apple the tech and music giant can't go after me for trademark infringement, though for music, computer tech and software they would have a case.