“Cantrip” is a Scottish dialect term that was first used in the sense of “a witch’s trick.” Since the 18th century, it has evolved from spellwork to be used to refer to a prank or another over-the-top act. The origin is undecided, but it might be an alteration of “caltrop,” which is any one of several plants that have stout spines on the fruit or flower heads, including star thistle, puncture vine, and water chestnut.