Nico ranks at #178 with 582 entries, and the name follows the same Italian-and-Spanish-coded male trajectory as Luca and Leo. It is a diminutive form (of Nicholas, Nicolás, or Niccolò) that has gone fully standalone in contemporary American naming.
The romance-language male cluster
Nico shares a register with Luca, Enzo, and Milo — short two-syllable male names with romance-language origin and open-vowel endings. These names tend to attract owners aged 25-40 who want something slightly distinctive without venturing into uncommon territory. Nico has the advantage of being instantly readable in English while keeping the Italian-Spanish texture intact.
One counter-reading: Nico the Velvet Underground singer and Nico Robin from One Piece are the two cultural anchors most likely to come up in conversation. Neither dominates pet naming, but the One Piece character has a real presence among anime-aware adopters in the 25-35 range. That subset tends to skew toward cats and small dogs rather than large breeds.
Where the name lands by breed
Nico over-indexes slightly on Italian Greyhounds and small Italian-coded breeds, but it lands across the full spectrum of mid-sized companions and cats at near-average rates. The name also sees solid use among shorthaired cats whose owners want a male name with European warmth without being too formal. The two-syllable shape with open ending (NEE-koh) carries well at distance and recalls cleanly, which makes it functional for off-leash work as well as polished for casual use. The Nicholas baby name page shows the formal version, which has been an SSA top-50 boys' name for decades and provides the foundation that the diminutive pet-naming tradition draws on across multiple language traditions and naming registers.