Wendy’s had the best frosties! I guess they still have them, though I recall them from my childhood, haven’t been in years. That was their claim to fame with me. They are too thick for a straw so they would give you a spoon with them.
Another frosty I recall was the frozen malt kind you got from the ice cream man. I used to keep a tube sock full of quarters for when he came around. Those frosties were made by Carnation and they were called malts. You’d eat them with a small flat “spoon.” These are the cool, sweet images the word frosty summons to my memory.