The name "Boxer" is supposedly derived from the breed's tendency to play by standing on its hind legs and "boxing" with its front paws. According to Andrew H. Brace's Pet owner's guide to the Boxer, this theory is the least plausible explanation.He claims "it's unlikely that a nation so permeated with nationalism would give to one of its most famous breeds a name so obviously anglicised".
German linguistic and historical evidence find the earliest written source for the word Boxer in the 18th century, where it is found in a text in the Deutsches Fremdwörterbuch (The German Dictionary of Foreign Words),which cites an author named Musäus of 1782 writing "daß er aus Furcht vor dem großen Baxer Salmonet ... sich auf einige Tage in ein geräumiges Packfaß ... absentiret hatte". At that time the spelling "baxer" equalled "boxer". Both the verb (boxen [English "to box, to punch, to jab"]) and the noun (Boxer) were common German words as early as the late 18th century. The term Boxl, also written Buxn or Buchsen in the Bavarian dialect, means "short (leather) trousers" or "underwear". The very similar-sounding term Boxerl, also from the Bavarian dialect, is an endearing term for Boxer.More in line with historical facts, Brace states that there exist many other theories to explain the origin of the breed name, from which he favors the one claiming the smaller Bullenbeisser (Brabanter) were also known as "Boxl" and that Boxer is just a corruption of that word.
In the same vein runs a theory based on the fact that there were a group of dogs known as Bierboxer in Munich by the time of the breed's development. These dogs were the result from mixes of Bullenbeisser and other similar breeds. Bier (beer) probably refers to the Biergarten, the typical Munich beergarden, an open-air restaurant where people used to take their dogs along. The nickname "Deutscher Boxer" was derived from bierboxer and Boxer could also be a corruption of the former or a contraction of the latter.
A passage from the book "The Complete Boxer" by Milo G Denlinger states:
It has been claimed that the name "Boxer" was jokingly applied by an English traveler who noted a tendency of the dog to use its paws in fighting. This seems improbable. Any such action would likely result in a badly bitten if not broken leg. On the other hand, a German breeder of forty years' experience states positively that the Boxer does not use his feet, except to try and extinguish a small flame such as a burning match. But a Boxer does box with his head. He will hit (not bite) a cat with his muzzle hard enough to knock it out and he will box a ball with his nose. Or perhaps, since the German dictionary translates 'boxer' as 'prize-fighter' the name was bestowed in appreciation of the fighting qualities of the breed rather than its technique.
Boxer is also the name of a dog owned by John Peerybingle, the main character on the best selling 1845 book The Cricket on the Hearth by Charles Dickens, which is evidence that "Boxer" was commonly used as a dog name by the early 19th century, before the establishment of the breed by the end of that same century.
The name of the breed could also be simply due to the names of the very first known specimens of the breed (Lechner's Box, for instance).