These have been around formally since the 1980s and the definition is the re-interpretation of a word as an acronym, or the re-interpretation of word that is already an acronym (sometimes for humorous purposes).
An example of the first meaning would be Ford as in motor car, named after Mr Ford. The backronym might be Fix Or Repair Daily.
An example of the second would be FIAT which is an acronym for Fabbrica Italiana Automobili Torino, the backronym is more amusingly:
Fix It Again Tony.
I’d like to make up a few of my own, starting with Condem and moving onto NAP…