Maximilian appears 65 times at rank 1595 on male pets. The name is a deliberate gesture toward imperial grandeur — it was borne by Holy Roman Emperors and Austrian archduke-turned-Mexican emperor Maximilian I — applied to a dog that the owner has decided deserves the full formal treatment rather than the shortened Max.
The Full Imperial Form
Maximilian is the expansion of Max taken to its most formal expression. Where Max is the most popular male dog name in American registries year after year, Maximilian is its rarer, more ceremonial ancestor. Owners who use the full form are making a statement about their dog's dignity. The human name is at /names/maximilian.
Breed and Owner Fit
Maximilian requires a large breed with physical presence. Great Danes and German Shepherds carry the imperial register naturally — the former is simply too large to have a nickname, and the latter has Germanic cultural coherence. The Maximilian I of Mexico connection is an odd historical layer that some owners find delightful. Max remains the daily nickname.
The Counter-Reading
Maximilian on a small dog is either deeply ironic or deeply committed to the bit. On a Great Dane, it's simply appropriate. The name's grandeur is its main risk — it sets an expectation that the dog either has to meet or delightfully fail. Most Maximilians manage both.