Hasn’t got a clue

With nautical origins, the clew refers to the corner of the sail where a brass ring is sewn into the fabric of the sail in order to properly hold the sail in place. If a clew should rip, the sail would loose shape and the vessel will not sail in a controlled manner. Until it is refastened, it ‘hasn’t got a clew,’ or needs to ‘get clewed up’ again. Today if someone ‘hasn’t got a clue’ then they do not understand or are not knowledgeable. To ‘get clued up’ is to learn about or to come to fully understand something. A nautical term that has now become part of everyday language