'back-formation' definitions:

Definition of 'back-formation'

From: WordNet
noun
A word invented (usually unwittingly by subtracting an affix) on the assumption that a familiar word derives from it

Definition of 'back-formation'

From: GCIDE
  • back-formation \back"-for*ma`tion\ n. (Linguistics)
  • 1. a word invented (usually unwittingly by subtracting an affix) on the assumption that a familiar word derives from it, such as emote from emotion. [WordNet 1.5 +PJC]
  • 2. the process of inventing a back-formation[1]. [PJC]