Partly because we could, and partly because it’s a cool word. My best guess as to what it means in context (and yes, I’m a very bad fanboy; I read issue one only because it was convenient, and have not yet read any subsequent issues) is that it’s being used as a peculiar synonym for Jotun (Mimir, the thrice-wise, was one). They were giants, Dawn got all big, that’s how the math appears to me today to work. There’s no clear indication, as far as my librarian and I can tell, that it means anything other than “really wise” in the original, but the Eddas are full of threes, so three wisdoms that we’re overlooking wouldn’t entirely surprise me.