“Contraction (noun): The shortening of word or phrase by omitting a letter or letters, especially within the word, and a curtailment reflected in its pronunciation; an internally truncated word or phrase, with the omitted letter or letters usually indicated by an apostrophe. Adjective: contractional, contractive; Verb: contract.
‘The word that excited Swift to greatest fury was mob, a vulgar contraction of mobile vulgus.’ Ernest Gowers, Plain Words.”
Excerpted from: Grambs, David. The Random House Dictionary for Writers and Readers. New York: Random House, 1990.