'shenanigan' is of uncertain origin; it likely entered American English in the mid-19th century and has been linked (perhaps folk-etymologically) to Irish Gaelic 'sionnachuighim' or 'sionnach' meaning 'fox' or the verb 'to play the fox' (i.e., to play tricks).

'shenanigan' appeared in U.S. sources in the 1850s–1870s, especially in frontier and mining communities. The word was used in forms like 'shenanigan' and plural 'shenanigans' and became standard slang for tricks or dishonest schemes.

Initially used for pranks or trickish behavior, the word's sense broadened to include deceitful or fraudulent actions; today it commonly refers to both harmless mischief and (in the plural) underhanded schemes.