The Rice University Neologisms Database

a phrase that has a “dirty” double entendre not intended by the speaker I believe this term was originally used because a double entendre can be seen as a sort of incorrectly understood (or classified) use of words. However, the word “misclassified” is not a noun, and the use of an adjectival phrase in situations I’ve heard the word “misclass” used would be far too bulky and awkward. Thus by dropping the -ified, which contains -ify (noun) + -ed (adjective), the word was shortened in such a way as to be appropriate for use “misclass situations.”