The word backronym (or bacronym) is a portmanteau (a combination or a blend) of backward and acronym, and has been defined as a “reverse acronym”.
Its earliest known citation in print is as “bacronym” (using just the b in backward attached to the beginning of acronym) in the November 1983 edition of the Washington Post monthly neologism contest. The newspaper quoted winning reader “Meredith G. Williams of Potomac” defining it as the “same as an acronym, except that the words were chosen to fit the letters”.
A backronym (or alternately bacronym) is a phrase constructed purposely, such that an acronym can be formed to a specific desired word. Backronyms may be invented with serious or humorous intent, or may be a type of false or folk etymology.