clue

Where it comes from

Clue ordinarily means information that helps someone solve a problem or mystery. Clue is a spelling variant of clew, an Old English and Middle English word for a ball or skein of thread or yarn. The word itself is Germanic; it did not come from Greek mythology. The story of Ariadne giving Theseus thread to retrace his path through the Labyrinth supplied the semantic bridge.

How the meaning developed

A clew became something that guides a person through difficulty, then a fact or piece of evidence that guides someone toward a solution.