The word 浴缸 is formed by directly combining two meaningful characters: 浴 (yù), which means "to bathe" or "bathing", and 缸 (gāng), which means a large, sturdy vessel or vat, typically made of pottery or ceramic. It is a straightforward, logical compound where the first character describes the purpose or action, and the second character specifies the type of object used for that purpose, creating the complete image and meaning of a "bathing vat" or bathtub.