1856, apparently an alteration of Scottish sculdudrie "adultery" (1713), sculduddery "bawdry, obscenity" (1821), a euphemism of uncertain origin.
Shady behavior; dirty work, hanky-panky
[1867+; a US alteration of Scots sculduddery, ''bawdry, obscenity,'' which is attested from the early 18th century]