RALPH: “Start” derives from an old German word storta which meant to knock something over out of surprise or shock. It’s related to our modern word, “startle.” 
DAVINA: In English, it originally meant to move suddenly, like someone jumping up from a concealed position to attack, or a surprised animal leaping up to flee a threat. 
RALPH: It was only around Shakespeare’s time that the word ‘start’ began to be used in its modern sense, to begin an activity. 
DAVINA: Here, Banquo asks why Macbeth is startled when the witches refer to him as a future king, which seems to Banquo a favorable, or fair, prediction. 
RALPH: Perhaps what seems a “fair” prophecy to Banquo has evoked a “foul” or dark thought in Macbeth.