An Etymological Dictionary of the German Language/Annotated/Bock
Bock, masculine, ‘buck, he-goat, ram,’ from the equivalent Middle High German bock (genitive bockes), Old High German boc, masculine; corresponds to Dutch bok, Anglo-Saxon bucca, English buck, Old Icelandic bukkr and bokkr (Gothic *bukks, *bukka, masculine) Like so many names of animals (compare e.g. Aue, Geiß), Bock too may have descended from primitively Aryan times; comp; Old Irish bocc, from primitively Keltic bucco-. Although it is not quite impossible that the whole Teutonic class was borrowed from Keltic, yet it seems more probable, on account of Armenian buc, ‘lamb,’ and Zend bûza, ‘he-goat’ (Aryan primitive form bhûga), that it was only primitively akin to Keltic French bouc may be derived from Teutonic or Keltic. Another Old Teutonic word (related to Latin caper, Greek κάπρος) is preserved in Modern High German Habergeiß. — Bock, ‘mistake,’ Modern High German only, seems to be a pun due to Modern High German Verstoß, ‘blunder.’ The origin of the phrase einen Bock schießen (‘to commit a blunder’) is not clear; note, however, that eine Lerche schießen is ‘to tall head over heels.’ — Bock (whence French boc), for Bockbier, which first occurs in Modern High German, is an abbrev. of Einbock (now Eimbocker Bier); compare the origin of Thaler.