ploy (n.)

1722, "anything with which one amuses oneself, a harmless frolic," Scottish and northern England dialect, possibly a shortened form of employ. Popularized in the sense of "move or gambit made to manipulate others and gain advantage" by British humorist Stephen Potter (1900-1969), who parodied self-help manuals in books such as 1947's "The Theory and Practice of Gamesmanship: Or the Art of Winning Games Without Actually Cheating."