The use of both most and the suffix -est to indicate the superlative form of an adjective or adverb. See also: double comparative.
Examples and Observations:
- "You can't say 'most stupidest.' Stupidest is not a word, and even if it were, it implies most."
(Haven Kimmel, A Girl Named Zippy, Doubleday, 2001) - "Mirror, mirror, on the wall, who's the most baddest angry young man of all?"
(Donald Barthelme, "Before the Mirror") - "Nabo told me de absolutely most funniest story this morning. I nearly spoiled myself with delight."
(Queen in Las Meninas by Lynn Nottage, in Crumbs From the Table of Joy, and Other Plays, Theatre Communications Group, 2004) - "Standard English no longer permits expressions such as most unkindest, where the superlative is marked by the preceding most as well as the -est inflection. In C16 there was no constraint on their use, and Shakespeare uses them in several of his plays to underscore a dramatic judgment. The use of most highest in religious discourse is similarly rhetorical and was exempted by some C18 grammarians (notably, Lowth, Bishop of London) from the general censure of double superlatives. Grammarians can certainly argue that one or other superlative marker is redundant, and in measured prose one of them would be edited out."
(Pam Peters, The Cambridge Guide to English Usage, Cambridge University Press, 2004) - "In profane authors there are also many instances of the use of the double superlative. Sir Thomas More used the expression, 'most basest'; Ben Jonson that of, 'most ancientest'; John Lilly (of the time of Queen Elizabeth) that of, 'most brightest'; and Shakespeare, 'most boldest, most unkindest, most heaviest.'"
("On the Language of Uneducated People," The Saturday Magazine, August 24, 1844)

