Bock is a style of lager beer which originated in Germany. It was
     traditionally brewed in the fall, at the end of the growing season,
     when barley and hops were at their peak. It was "lagered" all winter
     and enjoyed in the spring at the beginning of the new brewing season.
     Bocks can be pale (helles) or dark (dunkles) and there are
     double(doppel) bocks which are extra strong.

     Bocks are usually strong beers made with lots of malt yielding a very
     full-bodied, alcoholic beer. A persistent myth has been that bock
     beers are made from the dregs at the bottom of a barrel when they are
     cleaned in the spring. This probably seemed logical because of the
     heavier body and higher strength of bocks. From a brewing standpoint,
     this is clearly impossible for two reasons: 1) The "dregs" left after
     fermentation are unfermentable, which is exactly why they are left
     over. They cannot be fermented again to make more beer. 2) Any
     attempt to re-use the "dregs" would probably result in serious
     bacterial contamination and a product which does not resemble beer as
     we know it.