" The word 'clue' derives from 'clew', meaning a ball of thread or yarn. It had come to mean 'that which points the way' because of the Greek myth in which Theseus uses a ball of yarn, given to him by Ariadne, to find his way out of the Minotaur's labyrinth. "

― Kate Summerscale , The Suspicions of Mr. Whicher