So, I'm watching Star Trek: The Motion Picture the other night and - spoiler alert in case you haven't seen it - they say that Vger became Vger after landing on a machine planet that built it a ship and sent it home. That machine planet? BORG.
Though not directly addressed as such, there is some pretty good evidence that the machine planet that Voyager 6 encountered was, in fact, Borg in nature. We never see the planet in the movie (unless it's one of the models floating around the interior), but we do see Vger and the ship carrying it back to Earth.
First, we'll examine Vger's weaponry. Here's the clip from the beginning of the movie where Vger blasts itself some Klingons:
Skip ahead to 1:45 if you're impatient. Seem familiar? I tried to find a video that simply showed the plasma bolt being fired by a unimatrix in STO, but the internet is being uncooperative. You'll just have to do a Red Alert mission to see.
Secondly, however, is the ship carrying Vger itself. For most of the movie, all you can see of Vger is the nebulous cloud of energy surrounding it and some parts of the ship itself at so close a range as to be unidentifiable. That changes, however, once Vger reaches Earth and sheds the energy cloud. Then we can see that Vger looks like this:
What does that look like to you??
TOTALLY Borg. Vger ran into the Borg, they refit the machine and sent it back to Earth.
We're just lucky that Vger developed self-awareness. Otherwise, it'd been a lot less about meeting the creator and a whole lot more "resistance is futile". If not for Vger's self-awareness existential crisis, Earth could have been a Borg planet before good ol' Jean-Luc was in diapers.
Talk about dodging a bullet. LoL