Non Sequitur by Wiley Miller for January 27, 2017

“Skulduggery” today means “underhanded dealings,” “trickery” or “clandestine machinations.” The term is apparently an American invention, first appearing in print (as far as we know) in 1867 (“From Minnesota had been imported the mysterious term ‘scull-duggery’, used to signify political or other trickery.”), but since that quotation is an explanation of the term, we can assume it had been in use for some time before that. Today “sculduggery” is most often associated with cloak-and-dagger intelligence agencies such as the CIA, but freelancers and domestic political operatives have made their own splashes on occasion with “skulduggery”

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http://www.word-detective.com/2008/02/skulduggery/

I always thought it originally pertained to grave robbery, body snatching and guys like Burke and Hare !