I say that because 
and 
are considered the 'material' elements, so why not hypermaterial?
There's actually a totally reasonable and utterly unimportant reason for this. (skip if you don't care)
Hypermaterial materials are not just "thick" materials. They exist beyond (not outside) the realms of our dimension. For example, a Hypercube exists in 4 linear dimensions (time isn't a linear dimension). It isn't non-existant or merely in another realms; instead it extends far past ours into the other realms as well. The concept of having a "hypermaterial barrier" is that the aetherial, which utilize their ability to escape the normal realm, are blocked in those realms due to that exact ability.
Now I'm sure you're going to point out that it should block everything in every realm then. But the difference is that in other realms the wall need not be potent, because the aetherial creatures, while transpiring this realm to others for the purpose of evading difficulties in this realm, do not actually engage in behavior in the other realms (those are reserved for this realm). It's essentially like a bear sticking his face into the water. He's beyond the realm of the salmon, but his behavior is in their realm. While in this state, he does not impact the materials of the world in which he actually lives. Thus, even a cheap flimsy wall in the other dimensions would block the aetherial creatures. But in this realm, such barriers, capable of blocking anything and everything, are not even reasonable but for short periods of time.
Besides all of that, I thought it was a snazy name.
