Have you ever heard of the Boxer dog? They're medium sized, short haired dogs that originated in Germany. 
I think I've seen them before. Do they have squarish, boxy-type heads?
Yes! They are a "brachycephalic" breed, which means they have a broad, short skull, square muzzle, and usually an underbite. 
I do know those dogs! I had no idea they came from Germany.
They were actually bred from the Old English Bulldog and another breed, the Bullenbeisser, which is now extinct due to the crossbreeding. 
That's interesting. Dog breeding is a topic that always fascinated me. I had no idea that some breeds went extinct!
Dog breed
Dog breeds are dogs that have relatively uniform physical characteristics developed by humans, with breeding animals selected for phenotypic traits such as size, coat color, structure, and behavior. The Fédération Cynologique Internationale recognizes 337 pure dog breeds.
Other uses of the term breed when referring to dogs may include pure breeds, cross-breeds, mixed breeds and natural breeds.
First dog breeds.
The domestic dog is the first species, and the only large carnivore, to have been domesticated. Over the past
Boxer (dog)
The Boxer is a medium-sized, short-haired breed of dog, developed in Germany. The coat is smooth and tight-fitting; colors are fawn brindled or white, with or without white markings. Boxers are brachycephalic (they have broad, short skulls), have a square muzzle, mandibular prognathism (an underbite), very strong jaws, and a powerful bite ideal for hanging on to large prey. The Boxer was bred from the Old English Bulldog and the now extinct Bullenbeisser