Millie is a moderately popular girls' name in England & Wales, ranking #140 in 1996 with 324 recorded births. The name reached its all-time peak in 2004 with 2,421 births ranking #22. In 1996, approximately 1 in every 914 girls born was named Millie. FALLING Recent data shows the name is currently falling.
Millie is a warm vintage short form that now often stands as a given name in its own right. Its exact traditional meaning depends on which longer name family sits behind it.
Its rise fits the broad return of nickname-style vintage names that feel affectionate and energetic. Millie works especially well because it is cheerful without feeling flimsy.