A liar was a derogatory rank or nickname given to a sailor assigned to clean the lowest-status areas of a ship, particularly the exterior hull, head, or beakhead. In historic naval tradition, this unpleasant duty was handed out as a punishment to a crew member caught lying or spreading false rumors during the previous week. The practice served as both a practical way to get dirty work done and a public shaming mechanism.
Heard on the job
He got caught spinning yarns to the mate, so he's playing the liar this week with a bucket and a brush.