Pet form of Millicent or Amelia — gentle strength; industrious. A Victorian nickname that returned as a full name in Britain in the 2000s.
Millie ranks 73rd among American girls in 2025, with 3,353 born that year. Its best year was 2025, when 3,353 babies were given the name, ranking 73rd. The typical living American called Millie is about 7 years old today. It is relatively most common in Wyoming, where it accounts for 0.58% of births.
Source: US Social Security Administration, national and state name files, 2025 release, and the Office for National Statistics for England and Wales. Etymology researched and written by our editors. Living-population and median-age figures are our own estimates, described in the methodology.