Mitzy is a variant spelling of Mitzi — the German nickname for Maria or Miriam — and it carries the same retro-glamour energy that's been quietly rehabilitating mid-century feminine nicknames. On a small female dog or a cat with an imperious air, Mitzy is the kind of name that sounds like it belongs in a black-and-white photograph.
The Mitzi Vintage Moment
Mitzi peaked as an American name in the 1940s and 1950s, associated with actresses and showgirls — a name with sequins on it. That vintage sparkle is exactly what makes it interesting again now. The -zy spelling (versus the traditional -zi) is a minor modernization that keeps the sound identical while signaling that the owner chose it deliberately rather than inherited it. Compare it to Fritzi and Liesl in the same German-diminutive category.
Breed and Size Fit
Mitzy is almost never given to large dogs — the name's delicate phonetics match the aesthetic of small breeds like Toy Poodles, Pomeranians, and Yorkies. It also works beautifully on Persian and Himalayan cats with the kind of diva energy the name implies.
The Counter-Reading: Too Frou-Frou for Some Owners
Mitzy reads as unambiguously feminine and unambiguously small-dog. If your Mitzy grows into a 60-pound dog, the name becomes ironic at best. Owners who want the vintage charm without the size-limitation implication might look at Millie or Mazie as alternatives.