skulduggery
A devious device or trick.
countable
A private company cannot get away with a skulduggery of that sort. Once it has paid out its money for taxes, it cannot reach into the public treasury and get it back and apply it on its amortization account.
Dishonest, underhanded, or unscrupulous activities or behaviour.
uncountable
And I have another reason which I will express to my St Paul friends, and that is, that they have always been controlled in their political action here by a class of men who have always some traps set for the country members—by men who are always up to this border ruffian kind of trickery—this kind of skullduggery, as it is called in Minnesota. And now St. Paul allows herself to be controlled by these same border ruffian politicians.
Where it comes from
An alteration of Scots sculduddery, sculdudrie (“adultery, unchaste behaviour; obscenity, lewdness”), of long-uncertain origin (probably a euphemism). Relation to skull is speculative at best and likely folk etymology. The American spelling skullduggery is in keeping with terms such as skillful and willful.
Adapted from the Wiktionary entry skulduggery (CC BY-SA 4.0).