From the sad reality of losing a cherished object down a sink or bathtub drain comes this idiom, meaning to do or attempt to do something that ultimately will be lost forever.

• 这个成语正是从把珍贵物品丢在了水池或浴缸的下水管里的现实中来，它的意思是“做或试图去做永远无法得到的事”。