frost·ing (frôstĭng, frŏstĭng)
1. Icing, as on a cake.
2. A roughened or speckled surface imparted to glass or metal.
Our Living Language Although both frosting and icing are widespread, people in New England, the Upper Midwest, and the West tend to put frosting on cake. In Pennsylvania, New Jersey, the Lower Midwest, and all of the South, the preferred term is icing. There is some overlap, especially in upstate New York, Michigan, and California, but the regions in which the two words predominate are surprisingly distinct. A few people in the South call it by a third name, filling, even when it goes on top.
The American Heritage® Dictionary of the English Language, Fifth Edition copyright ©2020 by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
Indo-European & Semitic Roots Appendices
Thousands of entries in the dictionary include etymologies that trace their origins back to reconstructed proto-languages. You can obtain more information about these forms in our online appendices:
The Indo-European appendix covers nearly half of the Indo-European roots that have left their mark on English words. A more complete treatment of Indo-European roots and the English words derived from them is available in our Dictionary of Indo-European Roots.