Milli is the double-L variant of Millie — a diminutive of Millicent or Mildred that also stands independently as a name. For a female pet, the -lli spelling gives it a slightly more playful visual character than the standard form, suggesting an owner who made a deliberate spelling choice rather than reaching for the default.
The Millie Family
Millie, Milly, and Milli all occupy the same sonic space: a warm two-syllable nickname-name with vintage English roots. Millie is the most common spelling in pet registries; Milli is the less frequent variant that reads as either a spelling preference or a nod to Milli Vanilli — the late-1980s pop duo whose Grammy win and lip-syncing scandal remains one of pop music's most memorable controversies. Either reading works, and neither requires explanation.
Breed and Temperament Fit
Milli suits small-to-medium female dogs with an expressive, sociable personality. Miniature Schnauzers and Cocker Spaniels wear it easily. For cats, the name lands particularly well on females who are assertively affectionate — the type that demands attention on their schedule.
The Counter-Reading: Spelling Creates Friction
The double-L spelling means consistent correction in written contexts — vet records, tags, boarding facilities. Most people will default to Millie. If the Milli spelling is important to the owner, they should be prepared to spell it out routinely for the animal's entire life.