Curtis is a surname-turned-first-name from Old French, meaning "courteous." It peaked as an American given name in the postwar decades without ever being fashionable. On a pet, it reads as warm retro: the name of someone's reliable dad, a steady side character in a 1970s sitcom.
The Mid-Century Everyman Appeal
Curtis shares register with Earl, Clifford, and Gerald: names that were genuinely common in postwar America and now carry nostalgia. The appeal for pet owners is a kind of reverse-prestige, choosing a name that's emphatically not trendy, that has a lived-in quality.
Human Name Crossover
Curtis is a fully functioning human name with consistent historical use. A dog named Curtis is a dog that feels like a person. It sits comfortably on Labrador Retrievers and Golden Retrievers.
The Counter-Reading: No Standout Quality
Curtis has no particularly strong association: no famous fictional dog, no vivid etymology, no striking sound. It's pleasant and forgettable, which explains the 39 registrations. It works well on a dog who doesn't need a name to make a statement.