Any strict definitions for the term “barleywine” are of fairly recent origin—and, according to respected beer historian Martyn Cornell, it’s dubious to apply the word to a style. For centuries, it was simply a poetic way of referring to the stronger sorts of pale-ish beers available in Britain. It didn’t appear on a label until about 1900, in connection with Bass Brewery’s No. 1, a 10-plus percent ABV Burton-style ale.
Its name notwithstanding, brewers have been making very strong beers for ages. Many were kept for a considerable period of time before release; others were sold as soon as they hit the cask. This crucial distinction was consistently applied: “Mild” simply meant an unaged beer, regardless of strength or color. “Old”—or, in some references, “stale” beers—were aged long enough to dry out and acquire a “vinous” character. The brewers didn’t want too much acidity, for which remedies abounded. Aging required at least a year, and in estate-brewed beers often much longer: A character in George Farquhar’s play The Beaux’ Stratagem (1707) described his ale: “’tis smooth as oil, sweet as milk, clear as amber, and strong as brandy; and will be just fourteen year old the fifth day of next March, old style.”
The Inner Life of Barrels
With porters and stouts, “vatted” meant aged versions, stored in large tanks rather than barrels. By the 1850s, Tizard uses “old” and “vatted” interchangeably and notes in his day a “general change in public taste in many places, from new to old.” His advice for vessels for “production of a pale, bright, aged, and sound article” is “underground tanks ... lined with slate, to contain from 500 to 5,000 barrels.”