acrophony

from WordNet (r) 3.0 (2006)

acrophony
    n 1: naming a letter of the alphabet by using a word whose
         initial sound is the sound represented by that letter

from The Collaborative International Dictionary of English v.0.48

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.
   [1913 Webster]