Itks a !ritish and US English differences, there are quite few words that spell differently in both.

It is spelt with one "n". Here is where the two "n's" originate from.

The Doberman was originally developed around 1890 by Karl Friedrich Louis Dobermann.

Here is a little more history about the breed.

Dobermans were first bred in the town of Apolda, in the German state of Thuringia around 1890, following the Franco-Prussian War by Karl Friedrich Louis Dobermann. Dobermann served in the dangerous role of local tax collector, and ran the Apolda dog pound. With access to dogs of many breeds, he aimed to create a breed that would be ideal for protecting him during his collections, which took him through many bandit-infested areas. He set out to breed a new type of dog that, in his opinion, would be the perfect combination of strength, loyalty, intelligence, and ferocity. Later, Otto Goeller and Philip Gruening continued to develop the breed to become the dog that is seen today. The breed is believed to have been created from several different breeds of dogs that had the characteristics that Dobermann was looking for, including the German Pinscher, the Beauceron, the Rottweiler, the Thuringian Sylvan Dog, the Greyhound, the Great Dane, the Weimaraner, the German Shorthaired Pointer, the Manchester Terrier and the Old German Shepherd Dog. The exact ratios of mixing, and even the exact breeds that were used, remain uncertain to this day, although many experts believe that the Doberman Pinscher is a combination of at least four of these breeds. The single exception is the documented crossing with the Greyhound and Manchester Terrier. It is also widely believed that the old German Shepherd gene pool was the single largest contributor to the Doberman breed. After Dobermann's death in 1894, the Germans named the breed Dobermann-pinscher in his honor, but a half century later dropped the pinscher on the grounds that this German word for terrier was no longer appropriate.