Source : Webster's Revised Unabridged Dictionary (1913)

Acrophony \A*croph"o*ny\, n. [Gr. 'a`kros extreme + ? sound.]
   The use of a picture symbol of an object to represent
   phonetically the initial sound of the name of the object.

Source : WordNet®

acrophony
     n : naming a letter of the alphabet by using a word whose
         initial sound is the sound represented by that letter