A form of money that has gone out of use is ?

The form of money that has gone out of use is commodity money. Commodity money is a type of currency that is made of a physical commodity with intrinsic value, such as gold, silver, or salt. In the past, people would use these commodities as a medium of exchange because they were valuable in and of themselves. However, as economies grew and became more complex, commodity money became impractical and inconvenient for day-to-day transactions. In its place, bank money and paper money emerged as more convenient forms of currency that are easier to handle and transact with. Today, most countries use fiat money, which is not backed by a physical commodity but by the government's guarantee of its value.