Grounding means lots of things and has accrued nuances over the last ~2400 years, (usually considered to have begun in a Socratic dialogue about virtue and the gods) so there's no definitive take. I use the word to mean: how do we understand one thing in terms of another [1] but a more approachable entry point might be Harnad (1990). [pdf]

Grounding is relevant wrt btc in that money gets bootstrapped from something. Money can achieve its coordination function via transacting only after market participants have the felt sense that it is money, otherwise there is no reason to transact it. You will recognize this as a differential equation: as it becomes to be felt to be money, it begins to be used in limited ways as money, which increases the felt sense that it is money. The "feeling of money-ness" is a result of the grounding process playing out, cyclically. And so:

Gold's moneyness is grounded in people valuing gold, wanting the stuff out of some primitive acquisitive impulse; and then, with that desire in place, what turns out to be the quite nice properties of gold allow it to transition to a practical, working money. My assertion is that, absent that initial grounding -- the appeal of gold, and then the auto-catalytic bootstrap of memetic desire -- its moneyness would have remained concealed.

(Or "withdrawn" in Heideggerian terms, which I believe to be a good lens that is never applied.

I'm also dicking around with an account that talks about btc as a signaling hormone vs as an "asset" -- the "asset" language is largely nonsensical, at least without abusing the intuitive idea of what "asset" means -- which brushes against some of these strands of argument. One day.)

Anyway, in summary, btc has acquired some minimal money-ness, grounded in speculation -- thanks to that, some smallish number of people have the felt sense that it's money-enough because they can sell it to get the kind of money you can buy things with directly [2] -- something close to this is George Selgin's view on btc. Although maybe it has evolved in few years since I heard him discus it publicly.

Going back to the original point, if you want to throw a rock, and have whoever you hit with that rock be someone who interacts w/ btc and feels it to be money, a more tangible bootstrapping into something is required. I think social is that thing, and due to the forces loose in the world, a de-centralized social layer with money built in seems like how it will be instantiated.

[1] Note: in the interests of readability I didn't hedge the shit out every statement with "I propose" or "I believe" or "in my opinion" etc., but it's worth being explicit that these are very non-standard takes about the philosophy of money, the cognitive science of value abstraction, etc.

[2] Yes, I know, circular economy etc etc. A rounding error.