The term 'hammer, anvil or stirrup' refers to three small bones in the inner ear that are involved in hearing. The first BONE is the hammer, also known as the malleus, which is four letters long and connects to the eardrum. The second BONE is the anvil, also known as the incus, which is seven letters long and connects the hammer to the stirrup. The third BONE is the stirrup, also known as the stapes, which is also seven letters long and connects the anvil to the inner ear. Together, these three bones form a chain of ossicles that transmit sound vibrations from the eardrum to the inner ear.