The name Millie is believed to be a diminutive or nickname of names that contain mil, such as Camilla, Milan, Mila and Milo. It can also come from the Slavic element milŭ, meaning "gracious" or "dear," or Old English element milde, meaning "gentle." Millie was a popular girl's name in the first half of the 20th century, but fell off the Social Security Administration's top 1,000 in 1966. It didn't return until 2009 and saw a spike in popularity since Millie Bobby Brown landed the role of Eleven in the Netflix series "Stranger Things." The name has now been a top-200 girl's name every year since 2020 and came two spots away from cracking the top-100 in 2023.
