(n) a correct expression that takes the place of a popular but incorrect expression, Example:he preferred his erroneous but pleasing mumpsimus to the correct sumpsimus
The Collaborative International Dictionary of English (GCIDE) v.0.53 Collaborative International Dictionary (GCIDE)
‖n. [ L., he undertook, pret. of L. assumere. See Assume. ] (Law) (a) A promise or undertaking, founded on a consideration. This promise may be oral or in writing not under seal. It may be express or implied. (b) An action to recover damages for a breach or nonperformance of a contract or promise, express or implied, oral or in writing not under seal. Common or indebitatus assumpsit is brought for the most part on an implied promise. Special assumpsit is founded on an express promise or undertaking. Wharton. [ 1913 Webster ]