COTTON-PICKING - as an adjective cotton-picking "is widespread as a term of disparagement. Damned, darned." From the "Dictionary of American Regional English," Volume 1 by Frederic G. Cassidy (1985, Belknap Press of Harvard University Press, Cambridge, Mass., and London, England).
I'm not entirely satisfied with the described origin and definition of the phrase, since it seems to have come into general useage here in the U.S. (I am sure it's an Americanism) in the mid-60's or 70's. A series of movies were made starring Burt Reynolds, the first being Smoky and the Bandit that employed, as a base for the story line (that was as thin as Aunt Nellie's housecoat) a "good ol' boy" from the South and the Citizen's Band (CB) radio jargon employed by trucker's. That, along with the rise in popularity (again, entirely incomprehensible) of the TV series The Dukes of Hazzard lent the accent's and colloquialisms to the general language. But, Hey!, who am I to argue with the Harvard University Press...