backronym

A backronym treats an already existing word as an acronym and expands its letters into the words of a phrase, and so is effectively an acrostic. The word is a portmanteau of back and acronym. Backronyms may be invented with either serious or humorous intent, or they may be a type of false etymology or folk etymology.

A normal acronym is a word derived from the initial letter(s) of the words of a phrase, such as radar from "RAdio Detection And Ranging". By contrast, a backronym is "an acronym deliberately formed from a phrase whose initial letters spell out a particular word or words, either to create a memorable name or as a fanciful explanation of a word's origin". Many fictional espionage organizations are backronyms, such as SPECTRE (special executive for counterintelligence, terrorism, revenge and extortion) from the James Bond franchise.