Английский Этимологический словарь - sockdolager

- 1830, "a decisive blow," fanciful formation from sock (v.) "hit hard;" also said to be a variant of doxology, on a notion of "finality." The meaning "something exceptional" is attested from 1838. Sockdologising was nearly the last word President Abraham Lincoln heard. During the performance of Tom Taylor's "Our American Cousin," assassin John Wilkes Booth (who knew the play well) waited for the line "Well, I guess I know enough to turn you inside out, you sockdologising old man-trap," and as the audience laughed, Booth fired the fatal shot.