skullduggery (n.) -- deceitful or dishonest manipulation; underhand scheming or behavior; hocus-pocus, humbug, subterfuge, skullduggery, slickness, trickery.
Interesting tidbit #1: jiggery-pokery and is a classic example of what’s called a double dactyl, a dactyl being a stressed syllable followed by two unstressed syllables; it’s named after the Greek word for finger, whose joints represent the three syllables. Another example of a double dactyls are higgledy-piggledy.
Interesting tidbit #2: Hugger-mugger and hanky panky are classic examples of a reduplicated word, one in which its two halves are very closely similar in form. Other examples include hoker-moker, helter-skelter, and hodge-podge.
Interesting tidbit #3: In the 18th century, skulduggery meant fornication, adultery, unchastity (hanky-panky). In the 19th century it seems to have shifted to a sense of obscenity and indecency in language. Later in the 19th friendly was changed again to its current meaning.