9 June 2020
Shenanigans (it’s usually in the plural nowadays, although early uses are often singular) are trickery or illicit machinations, or pranks and light-hearted deceptions. The origin is unknown. It arises in U.S. slang in the mid nineteenth century.
The earliest citation that I have found is from 10 January 1855 in the Portage County Democrat:
How can an intelligent man say of another, as a politician he is a base, corruptible scoundrel, as a man, a fine, honorable, honest gentleman.
This looks like “shenanigan” to outsiders.
Several of the earliest citations are clustered in California, for example this one from the June 1855 issue of The Pioneer:
It seems that some three years since, Mr. Moon—Mr. John Moon, “Professor,” as he is styled in his bills, “Professor of Dexterity and Optical Deceptions, Fellow of the Mystic Lodge of Arts, London,” now one of the “Ethiopian Fakir Troupe” performing at the San Francisco Theater [...] An individual from “Pike County,” who had attended several evening and witnessed the “experiment,” suspected, in the classic language of the times, that there was something of “shenanigan” in it.
The quotation marks around both of these uses indicate that the term was new, at least to the editors. So, if antedatings are found, they are not likely to be much older than 1855.
Green’s Dictionary of Slang speculates on two possible origins. It could be from the Irish sionnach, meaning literally a fox but could be used metaphorically to refer to trickery or hiding, or it might be from the East Anglian dialectal nannicking, meaning fooling around or playing the fool. Wright’s English Dialect Dictionary defines nannick as “to play the fool; to play when one should be working; to idle away one’s time; to fidget.” And it defines nannicking as “full of apish tricks; trifling.” It isn’t far-fetched to think a phrase like is nannicking might become shenanigan. But these are just guesses, with no evidence behind either.
Sources:
“Editor’s Table.” The Pioneer; or, California Monthly Magazine, June 1855, 374. ProQuest.
Green’s Dictionary of Slang, 2020, s.v. shenanigan n.
“Our Correspondence.” Portage County Democrat (Ravenna, Ohio), 10 January 1855, 2. NewsBank: America’s Historical Newspapers.
Oxford English Dictionary, second edition, 1989, s.v. shenanigan, n.
Wright, Joseph. The English Dialect Dictionary, vol 4 of 6. Oxford: Henry Frowde, 1905, 225.