In TAS: More Tribbles, More Troubles,
the infertile tribbles were shown forming collectives.
I think the OP missed the obvious: Tribbles are the Borg.
Tribbles probably formed the First Collective as a defense, during the Klingon invasion of the tribble homeworld. The Klingons thought they destroyed that gargantuan fluffy nightmare—which had achieved consciousness itself—but it really fell into what they used to call a black hole. That formed when all the Klingon torpedoes detonated together in one spot. And emerged on the other side of the galaxy. It began assimilating bipedal species soon after, because it needed feet since it needed boots, in order to pull itself up by its own bootstraps.
And now, it's back.