A backronym (or bacronym or also retronym) is a phrase that is constructed "after the fact" from a previously existing word or abbreviation, the abbreviation being an initialism or an acronym. The term is a false acronym, and sometimes used to refer to the initialism or acronym itself, but usually in those cases, it is a "replacement" backronym, the abbreviation already having an associated phrase. When the backronym phrase becomes more popular than the original, the word becomes an anacronym. (But other than that, backronyms and anacronyms have little to do with each other.)
An example of a backronym from the word acronym is as follows.
- Acronyms Condense Representations Of Neologisms You Memorize
In this example, because the word acronym itself is not an acronym, the phrase above is a pure backronym, not a replacement backronym. Since the phrase indirectly refers to the word itself, it is also apronymic. If this backronym helps you remember the word acronym or backronym, then it is also a mnemonic.