Seymour lands at rank 1617 with 64 male pet registrations. It's a surname-turned-given-name with an Old French-via-English origin, and it carries the particular charm of names that were common in the early twentieth century, disappeared for decades, and are now being reconsidered with fresh appreciation.
The Vintage Revival Register
Seymour belongs with Mortimer, Reginald, and Archibald: Victorian-era names that feel both stuffy and endearing. On a dog, the stiffness becomes a joke the dog is always in on. Owners who choose Seymour tend to lean into the contrast — a small scrappy terrier named Seymour has a readymade character arc. The human name comparison is at /names/seymour.
The Pop-Culture Thread
Seymour Skinner from The Simpsons is probably the most familiar contemporary bearer: uptight, earnest, ultimately sympathetic. Seymour from Little Shop of Horrors is the other touchstone — nerdy, kind-hearted, in over his head. Both associations skew gentle rather than aggressive, which is useful context for a pet name: Seymour reads as a dog who has opinions but won't act on them.
The Counter-Reading
Seymour is genuinely uncommon at the vet's office, which means it lands as distinctive without being pretentious. The main friction is that people will sometimes hear "Simon" and need a correction. A reasonable price for a name this good.