back-formation

noun2

1. •
   The process by which a new word is formed from an older word by interpreting the former as a derivative of the latter, often by removing a morpheme (real or perceived) from the older word, such as the verb burgle, formed by removing -ar (perceived as an agent-noun suffix) from burglar.
2. •
   A word created in this way.

   • Back-formations, such as tambour (for “play the tambourine”), are a staple of comedic wordplay.