Coco is the only name in the top 10 that isn't really a human name — and it is also the only name in the top 10 that wins the Chihuahua category outright. She is #1 among Chihuahuas in our NYC and Seattle data with 394 entries, #2 among Yorkies, and #3 among Shih Tzus. There is no other top-10 name with this concentrated a small-dog signature.
What "not a human name" actually buys you
Most people don't think consciously about whether the name they're picking for a pet is also a baby name, but the decision shows up in the data. Owners who want a pet name that sounds like a pet name — without the worry that they're naming the cat after a coworker's daughter — gravitate toward names like Coco, Biscuit, Pickle, Olive. Coco sits at the most popular end of that pool. She doesn't compete with the human Coco demographically, because the human Coco barely exists in the SSA data at all.
That gives the name a strange privilege. Owners can use it without any of the social negotiation that goes into picking a name like Lucy or Charlie, where the baby-name version is also climbing. There is no mother-in-law saying "oh, like my sister." There is no kindergarten classroom association. Coco just lives in the pet world, doing pet things.
Two cultural reference points doing different work
The first is Coco Chanel. The reference is glamorous, sophisticated, French — and the owners pulling on that thread tend to give it to long-haired toy breeds with show-dog energy. Maltese, fluffy white Yorkie, the Pomeranian who knows she's pretty. The second is Pixar's Coco from 2017, which gave the name a warmer family register and pulled it into Latino and bilingual households more visibly. Those two references coexist now without conflict because owners simply don't think about which one they're invoking.
The Pixar association almost certainly broadened Coco's appeal in bilingual and Latino-American households — the film's Mexican setting and family register gave the name a warmth the Chanel reference alone never carried.
The doubled-syllable phonetic case
"Co-co" repeats the same syllable twice — a structure that is unusually common in pet names but rare in baby names. Mimi, Lulu, Bibi, Gigi, Fifi, Coco. The repetition has a specific function: it sounds like baby talk, and baby talk is exactly the register in which most pet owners speak to small companion animals. The name builds the relationship into its phonetics. That is why Coco is so concentrated in toy breeds, where the owner-pet vocal register is already pitched higher and more affectionate. On a 70-pound Lab, Coco would land differently. Owners feel that, even if they can't articulate it.