" Properly, an acronym is a word that is created from the initial letters or major parts of a compound term whose pronunciation is a word (“NAY-toe,” “SNAF-oo”), and an initialism is an abbreviation created from the initial letters of a compound term, like “FBI,” whose pronunciation is a collection of letters (“EFF BEE EYE”). “Acronym” gets used of both of these, however, and such use burns the biscuits of some. "

― Kory Stamper , Word by Word: The Secret Life of Dictionaries