How did the word ‘clue’ originate?

The word ‘clue’ derives from the Middle English word ‘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 made it back out of the deadly Minotaur’s (half-man, half-bull) labyrinth by unravelling a ball of yarn so he could retrace his steps. He used the “clew” as a guide (clue) to find a solution to his problem. This is why one is said to ‘unravel the clues’ of a mystery.