Nicholas at rank 1397 is the full formal deployment of a name that most dogs carry as Nick, and choosing the unabbreviated version is the entire aesthetic statement. It's part of the full-given-name-for-pets tradition, where the formality is the joke, the charm, and the intention all at once.
The Full-Formal-Name Move
Nicholas is a Greek name meaning victory of the people, from nike (victory) and laos (people). It's one of the most historically distributed names in European history, and the original Saint Nicholas' evolution into Santa Claus is one of naming culture's great transformations. On a dog, Nicholas signals the full-formal aesthetic: this dog has a name on its paperwork that sounds like it belongs to a tax attorney, and that is exactly the point. Standard Poodles and Dachshunds carry this dignity particularly well.
The Nick Shorthand
Nicholas on the license with Nick as the call name is the most common configuration. Nick is punchy, single-syllable, and clear. The human name is documented at /names/nicholas. Nick alone is an option, but it loses the joke that the full form provides.
The Counter-Reading
Nicholas on a dog inevitably invites the Santa question, especially in December. Owners prepared to lean into that seasonally will find it charming; owners who are not may find it tiring by year three.