hoar frost vs icing

hoar frost

noun
  • Originally, any frozen dew forming a white deposit on exposed surfaces. 

  • Water vapour which has undergone deposition or desublimation (“transformation directly into ice crystals without first turning into liquid water”) when the air is cold and moist to form a white deposit on exposed surfaces. 

icing

noun
  • The process of forming a layer of ice on a surface. 

  • A sweet, often creamy and thick glaze made primarily of sugar, often enriched with ingredients like butter, egg whites, or flavorings, typically used for baked goods. 

  • A minor violation of ice hockey rules, occurring when a player shoots the puck from his/her side of the red line so that it crosses the goal line on the opponent's side. A team playing short-handed is not penalized for this. 

  • Conditions conducive to the formation of ice on aircraft surfaces. 

How often have the words hoar frost and icing occurred in a corpus of books? (source: Google Ngram Viewer )