Metathesis is the transpotion of sounds in a word, as in the childish pronunciation of Pasketti for Spaghetti, and Homer Simpson's pronounciation of "noo-kyu-lar" for "nuclear." Metathesis has been responsible for a few genuine words in English, "butterfly" from "flutterby," and "sideburns" from "Burnsides," but it rarely rises to the level of a bonafide figure of speech. A rather nice simile, "calm as a clam," benefits from its metathesis, and the Reverend Spooner, (from whom Spoonerism, the transposition of initial consonant sounds) gave us wonderful methatheses such as "half warmed fishes" for "half formed wishes," but mostly metathesis is the provence of mispronunciation and the Freudian slip.
