British Dictionary definitions for icing on the cake
Word Origin and History for icing on the cake
1610s as an action; 1756 as a substance; meaning "cake icing" is from 1858; verbal noun from frost (v.).
Idioms and Phrases with icing on the cake
icing on the cake
Also, frosting on the cake. An additional benefit to something already good. For example, All these letters of congratulation are icing on the cake, or After that beautiful sunrise, the rainbow is just frosting on the cake. This metaphoric expression alludes to the sweet creamy coating used to enhance a cake. [Mid-1900s]