A Speed Bump cartoon from a little while ago, found on Pinterest:
The patient in the doctor’s office is — remember, this is Cartoon World — a gingerbread man, complaining of a sore knee. This sets things up for a play on the ambiguity of the verb form icing, related to either one of two verbs ice; one of them is related to the mass noun icing (in the U.S., parallel to frosting). From NOAD2 on this mass noun:
a mixture of sugar with liquid or butter, typically flavored and colored, and used as a coating for cakes or cookies
This substance mass noun icing and the verb ice ‘to decorate a cake with icing’ are in a very close synchronic relationship, so close that it’s hard to say which is basic and which derived (note: the verb could be back-derived from the noun); the history looks equally unclear, and the same relationships hold (in the U.S.) between the mass noun frosting and the verb frost (as in frost the cake). Somewhere in all of this is a metaphor relating the appearance of the cake-decorating substance to the appearance of accumulations of ice or frost.
The other verb ice, not well covered in the dictionaries I’ve looked at, is a at root a simple verbing of the noun ice referring to frozen water and meaning roughly ‘chill with ice’, but specialized in reference to ice therapy for sore muscles or joints. (I have joint problems all over the place, and so have cold packs to use for icing these joints.)