Originally, the adjective stout meant "proud" or "brave", but later, after the 14th century, it took on the connotation of "strong". The first known use of the word stout for beer was in a document dated 1677 found in the Egerton Manuscript,[4] the sense being that a stout beer was a strong beer. The expression stout porter was applied during the 18th century to strong versions of porter, and was used by Guinness of Ireland in 1820 – although Guinness had been brewing porters since about 1780, having originally been an ale brewer from its foundation in 1759. Stout still meant only "strong" and it could be related to any kind of beer, as long as it was strong: in the UK it was possible to find "stout pale ale", for example. Later, stout was eventually to be associated only with porter, becoming a synonym of dark beer. During the last part of the 19th century, stout porter beer gained the reputation of being a healthful, strengthening drink, so that it was used by athletes and nursing mothers, while doctors often recommended it to help recovery.[10]
Because of the huge popularity of porters, brewers made them in a variety of strengths. The beers with higher gravities were called "Stout Porters". There is still division and debate on whether stouts should be a separate style from porter. Usually the only deciding factor is strength.[11]