In Greek mythology, the minotaur was a terrible Cretan monster with the body of a man and the head of a bull who ate human flesh. He lived in a labyrinth on the island of Crete, and from time to time humans were sent into the labyrinth, where they could not find their way out, and the minotaur eventually ate them.

It happened that the city of Athens was required to send seven young men and seven maidens to Crete every ninth year to be sacrificed to the minotaur. When the third sacrifice came around, a certain Theseus volunteered to go in the hopes of killing the minotaur and ending Athens' tribute.

When Theseus reached Crete, he met Ariadne, the daughter of Minos, and Ariadne fell in love with him. Before Theseus entered the labyrinth, Ariadne gave him a ball of thread to guide him through the mazes of the labyrinth. In ancient Greek, this ball of thread was called a "clue." Theseus carried the clue of string with him, and as he walked, he unraveled the clue, leaving a trail to show how he had come in.

Theseus did kill the minotaur, and the clue he had left allowed him to safely find his way out of the labyrinth afterwards.

The word clue, literally a ball of thread, has taken many twists and turns through its history. In Old English it was cliwen, and later clew, and finally our current clue.

Fun fact: According to The Guinness Book of Music Facts and Feats, the world's shortest opera is The Deliverance of Theseus by Darius Milhaud. It lasts a mere 7 minutes, 27 seconds.