Bock beer may be the only style in the world with a mascot, the billy goat. Bock is German for goat. It is believed to be a corruption of Einbeck, reputed birthplace of the style.
The primary sensation of a bock beer is malt, not sweet caramel flavors, but the deeply satisfying dense, rich toasted flavor of Munich malt. Hops exist to cut the sweetness. The lager yeast and long cold storage ensures a minimum of fruity esters. The finish, while lightly sweet, is not cloying.
In response to the growing popularity of helles and pils beer, modern bock brewers began producing “maibock” or “helles bock,” a golden, slightly hoppy, bock-style beer. Still malty and rich tasting, the extra dose of hops snaps the palate to attention.
The bock tank-cleaning myth may come from an old American brewers' effort to promote bock as a springtime special. Devotees of the style would buy cases of bock during its limited availability to last through the year.
Born out of the monasteries, doppelbocks served as nutrition during Lenten fasts. The beers retained more sugar and nutrients and served as liquid bread for the monks. Ranging from 7 to 10 percent ABV, these beers are intense versions of a bock, bready, rich, and with hints of chocolate, but without any overt roasted coffee notes.
The most fearsome member of the bock family is the eisbock. A brewer mistakenly left a cask of doppelbock outside during a freezing winter night. Dismayed, the brewery staff went to dump the beer, but discovered a core of concentrated rich beer. Thanks to water freezing, the beer lost water, but no ethanol. Whether or not the federal authorities consider freezing a form of distillation (that is, illegal concentration) is contested, but few eisbocks come to the United States.