I’m happy to see people thinking about this, but I think that the existence of Meta’s Threads makes any use of the word “thread” an unnecessary association with Meta, if not an outright advertisement. Deeper meaning has, historically, never been as important for controlling how a term is used as sheer numbers. Way more people are using “Threads” to refer to the Meta product than are talking about the fediverse at all, and none of them are going to care why we should have dibs on “thread” as part of our name. They’ll just go, “threadiverse? Is that like Threads? Threads is just ads, I don’t know why you’d want to use it.”
As an alternative, I like “forumverse,” because Lemmy and kbin remind me of old-school forums, and it still links up with “fediverse” because of the “verse,” and because the word has the same rhythm. But I usually just tell my friends I’m on Lemmy, since I browse through a Lemmy instance, and that greatly influences my experience. I don’t mind adding that Lemmy is just one platform for accessing the same content, because it launches me into an explanation of how this is not a corporation-owned discussion space.