E. Cobham Brewer 18101897. Dictionary of Phrase and Fable. 1898.
Either a stone jar or a prison. The Greek word εo (kermos) means either an earthen jar or a prison, as in ε ε ε (chalko en keram), in a brazen prison. When Venus complained to the immortals that Diomed had wounded her, Din bade
her cheer up, for other immortals had suffered also, but had borne up under their affliction; as Mars, for example, when Otos and Ephialts bound him and kept him for thirteen months ε ε ε (in a brazen prison, or brazen jug). (Homer: Iliad, v. 381, etc.; see also ix. 469.) Ewing says keramos, potters earth or pottery, was also a prison, because prisoners were made to work up potters earth into jugs and other vessels. Thus we say, He was sent to the treadmill, meaning, to prison to work in the treadmill.