A cask deposit is a type of financial instrument that involves depositing money into a cask, or container, for safekeeping. The term 'TARTAR' is a six-letter word used to describe this type of deposit. It is derived from the Latin word 'TARTARUS, ' which means 'a place of confinement.' Cask deposits are often used by banks and other financial institutions to store large amounts of money securely. They are also used by individuals to store valuable items such as jewelry or documents.