Whenever I hear or read the word afoot I think of the famed fictional detective Sherlock Holmes, who said “the game is afoot” when beginning at least one or two of his adventures that I remember reading.
But to give credit to Sherlock Holmes, or more accurately the author of the Sherlock Holmes mysteries, Sir Arthur Conan Doyle, is probably a mistake. He was likely quoting William Shakespeare. In his play Henry V, Shakespeare has King Henry say, “The game’s afoot. Follow your spirit, and upon this charge cry, “God for Harry! England and Saint George!’”
Afoot means in preparation or in action.
Afoot can also mean on foot as in “he was walking afoot rather than crawling on knees.” However, that sense of the word is much less storied, so enough said.