Inappropriability refers to the idea, that certain things in this world are not prone to be converted into property. They are meant to be inappropriable. But saying that "x or y is inappropriable", sounds as if we were speaking about the 'ability' of a thing, whereas inappropriability refers to a social norm, to something we ought to do.
"As a principle, commons define a norm of inappropriability. This indeed requires establishing all social relationships anew, with this idea as a starting point: Inappropriability does not mean… that it would be impossible to appropriate something, but that it is socially unacceptable to appropriate it. In other words, that appropriating something as one’s private property is not permitted because that thing is reserved for common use.” (Dardot and Laval 2014: 583)
The problem is, that human beings are excellent appropriators. We are "able" to appropriate near to everything, and in fact near to everything in the world has been appropriated.
To appropriate something is not a problem per se. We can take care of it, share it with others, further evolve and nurture it, and yet: appropriation is a conditio sine qua non, an act from which many problems derive.
Appropriation makes things tradable. If we "buy and sell", we basically transfer property rights. We shape our world, our institutions and our governance principles according to the the idea that everything is owned by somebody. If not: things are taylored to be appropriated.
Because only if you own (dominate) something you can decide who accesses, uses, modifies or alienates it Alienation means: selling, giving away or passing on.
The same way appropriation enables/enacts alienation, the norm of "inapprobriability" is meant to enact practices which require that certain things are inalienable, i.e. cannot or hardly be sold.
What if work, land and knowledge, which can easily be unqualified for individual appropriation, would be declared "unapprobriable" by default? This would change everything.
Inappropriability precedes inalienability, which in turn precedes Pool, Cap & Divide Up or Pool, Cap & Mutualize.
# Storify
I don't have the information at hand, but you hopefully get the idea.
1000 years ago human beings could hardly imagine to individually appropriate XY - since ... we can. 500 years ago we could hardly imagine to individiually own xy. Since ... we can. 200 years ago we could hardly imagine to individually own a vaccine. 50 years ago we could hardly imagine to individually own a plant/ a genetic sequence/ a chemical substance or e Today we can imagine to individually appropriate the minerals on the moon and the mangenese nodules on Human beings will bring down the notion of "appropriability" to the nano-scale. Because, as Richard Feynman put it:
"There is plenty of space on the bottom."
xxxxxx
quote retrieved from "Patterns of Commoning", last paragraph html 
# See also Imprescriptibility