FYI, the thread highlighted here is still continuing, though one wonders if it might be losing utility!

The following is offered only as a laugh, and truly no offense intended to the originator. At times, the distance between mind and keyboard can be dauntingly immense:

The first forcing is unknown; the second forcing is also unknown; I fail to see where you have an unknown unknown. We suspect that something undefined going on: that we know. If we know that there must be something there, we know at least that. Something is known there. Knowledge is something we know, not something we don’t. So what is called the “unknown unknown” is actually a known (unknown) unknown. God knows what you can do with unknown unknown unknowns. A known unknown unknown is not very different from a known unknown, unless you come up with a very intriguing epistemic logic. The distinction is interesting if you’re a Secretary of defense indulging in spelling out a Johari window. Strictly speaking, the only thing you can say about unknown unknown is that we don’t know nothing about that. And even that, we know.

and no, context does not help that comment!