[Nevermark]

We know we can't see it (dark, as in not emitting or otherwise interacting with light), and it creates and responds to gravity in the exact same way the matter particles we know do (matter).

The two word choices can be quibbled with, but they form an accurate shorthand for what we know.

If the fine structure is discovered to be wrinkles in space I expect there will be a renaming during a time of great celebration by the future Nobel Prize winners! Especially if that also shone light on space-time's ultimate structure!

Edit: I will humbly propose a name for your postulated tiny space wrinkles: Wrinky-dinks!