The word "回笼" is formed by combining the character "回", meaning to return or go back, with "笼", meaning a cage or steamer. This combination creates a literal sense of returning something to a confined space, leading to specific meanings such as re-steaming food by placing it back into a steamer or withdrawing currency from circulation by metaphorically returning it to a restrained state. The formation is based on the direct relationship between the actions and objects denoted by the individual characters.