is there an Anglo-Saxon word at all that expresses this? Or is the mysterious quality and status of an import word something we can only express with other (meaning-modified) import words?
There's always the fallback to the the word "whatever", in all it's various intonations. It's like the "white flag of surrender" signaling a complete failure of vocabulary. That, and the loss in some conversations of verbs to express speech. I've overheard conversations very similar to this one: "I'm all, whatever, and he goes, whatever, we're like, you know, whatever."

(I seem to be feeling particulary grinchy this morning - time for a bike ride in the cold fog! What happened to spring? We went straight from winter rain to summer gloom and fog )