Hoarfrost is the light covering of white that forms when dew freezes. The word “hoar” comes from a Middle English term that means “gray or old.” The inspiration for “hoarfrost” came from the appearance of trees and bushes covered in frost that looks like white hair. While it’s most often seen outside on cold mornings, it can occur in any situation where there’s excess moisture that quickly freezes, such as in a freezer.