What is the X in X-mas?
"snow squall" 1828, American English, with earlier senses of "commotion," etc., dating to 1680s; perhaps imitative, or else from 17c. flurr "to scatter, fly with a whirring noise," perhaps from Middle English flouren "to sprinkle, as with flour" (late 14c.).
1757 in the commotion sense, from flurry (n.); 1883 in the snow sense. Related: Flurried; flurries; flurrying.