Maddie ranks at #194 with 552 entries, and the name follows the same diminutive-as-given pattern that Izzy works a few ranks higher. Maddie is the everyday call name for Madeline, Madison, Madelyn, or Maddison, and it occasionally functions as a standalone given name too.
The diminutive cluster, female edition
Maddie shares a register with Sadie, Lucy, and Izzy — two-syllable -ee ending female names that read as friendly and slightly informal. Owners who pick Maddie are usually not consciously naming after a specific person; the name has a generic warmth that pet owners default to when they want something that sounds like a real name without committing to formality.
One counter-reading: a meaningful subset of pet Maddies are named after a specific person — a daughter who has the name, a Madeline-from-the-children's-book reference, a Madison who could not be used because the human child has it. Those naming-by-tribute Maddies tend to land on small companions and family dogs where the affectionate transfer makes sense.
Where the name lands by breed
Small companions, family-coded retrievers, and mid-sized mixed breeds carry Maddie at near-average rates. Cats use the name at lower rates than for adjacent female names like Luna, partly because the diminutive register reads more dog-coded than cat-coded in our data. The Madeline baby name page shows the formal version, which has been an SSA top-100 girls' name for over a decade. Owners cross-shopping similar diminutive-style female names usually consider Sadie and Lucy alongside Maddie, picking based on which sound fits their household best and which one sounds best in everyday call cadence with the rest of the family's names.