Stout was first documented in the 17th century and was a term used to describe a very strong beer. Dark beers called porters were very popular at the time and brewers began experimenting with porters of different strengths. Those containing roughly seven or eight percent alcohol by volume, among the strongest porters, were known as stout porters. However, it would take quite a while for these porters to be known only as stouts. Even one of the world’s most recognizable stouts, Guinness, was once called a porter.
Stouts are distinguishable from porters in their ingredients. Porters use roast malted barley, according to Renegade Brewing. Stouts are made from black patent malt. Stouts are further classified into “milk” or “dry” stouts. Milk stout is a stout sweetened with lactose. Dry stouts are more bitter. Stouts also may be named as chocolate stout, oyster stout or oatmeal stout, depending on the ingredients used in the brewing process.