What are words called when they can be made from the sounds of letter names?

For example:

• Icy → IC

• Excel → XL

• Easy → EZ*

* This spelling is based upon the U.S.A's. more recent pronunciation of the letter Z, which is /ziː/, rather than the British style /zed/. Compare with the pronunciation of easy, which is /iːzi/ in both regions. See: O.A.L.D.

Solution 1:

Such a word is called a gramogram, also spelled grammagram, or letteral word. They are a subset of rebuses, as Stefan mentioned.

Wikipedia specifically describes a gramogram as

a letter or group of letters which can be pronounced to form one or more words

This may seem to indicate that only the combinations of letters may be called gramograms, but three (1, 2, 3) references on the page use gramogram to describe the words themselves.

Note that neither spelling of gramogram appears in the OED and only draw just over 5000 Google results combined (see gramogram results; grammagram results). So it does not appear to be a widely recognized term.

However, I did find two relevant results used in books, both by Rod L. Evans

• Tyrannosaurus Lex: The Marvelous Book of Palindromes, Anagrams, and Other Delightful and Outrageous Wordplay
• Thingamajigs and Whatchamacallits: Unfamiliar Terms for Familiar Things