You searched for: “acrophonies
acrophony (s) (noun), acrophonies (pl)
The sound of the "initial" or "beginning" of what was originally a picture-symbol or hieroglyph of an object to represent phonetically the initial syllable or sound of the name of the object; One example of acrophony can be the employment of the symbol of an ox, aleph, to represent the syllable or letter.

An acrophony can be said to be the naming of a letter by a word whose initial sound is the same as that which the letter represents.