back-formation (n.)

A term used in historical studies of MORPHOLOGY to refer to an abnormal type of WORD-FORMATION where a shorter word is derived by deleting an imagined AFFIX from a longer form already present in the language. Edit, for example, comes from editor, and not the other way round. This derivation presumably took place because NATIVE-SPEAKERS saw an ANALOGY between editor and other words where a normal derivational process had taken place, e.g. credit/creditor, inspect/inspector, act/actor, the NOUNS being in each case formed from the VERBS. The derivation of edit thus reverses the expected derivational pattern, hence the term ‘back-formation’.