The word 背包 (bēibāo) is formed by directly combining two meaningful characters: 背 (bēi), which means "to carry on the back", and 包 (bāo), which means "bag" or "sack". The formation is conceptually straightforward, it describes an object by its primary function and form. By placing these characters together, the term creates a clear mental picture of a specific kind of bag defined by how it is used: a bag you carry on your back, hence a backpack.