Slangy Slacks are a type of casual trousers that have become popular in recent years. They are usually made of lightweight, stretchy fabric and feature a relaxed fit. The term 'slangy' refers to the informal, laid-back style of the trousers. The term 'SLACK' is derived from the Old English word 'slacke, ' which means loose or SLACK. TROU is an abbreviation for trousers, which is another name for pants.