What is 'hoar' frost, and where does the name come from?
The word 'hoar' comes from what's called old 'high' German...and it means either gray or magnificent. One reference compares it to an old man's stately beard. Hoar frost crystals are 'gray' or 'silver' in color, and can be magnificent. They form when humidity is fairly high and temperatures drop below freezing. Small ice crystals on the ground, tree branches, etc. grow larger as the crystallization process continues with the added water vapor...perhaps in the way years of growth can add to a seniors' beard!