The term 'stay behind' can be broken down into five words: SHADOW, REMAIN, REIN, LAG, and TAIL. SHADOW is a verb meaning to follow or observe someone or something closely. REMAIN is a verb meaning to stay in the same place or condition. REIN is a noun meaning a long, thin strap attached to a bridle or harness and used to control a horse or other animal. LAG is a verb meaning to move or develop more slowly than others. TAIL is a noun meaning the rear part of an animal or object. Together, these words describe the act of staying behind or lagging behind someone or something.