The name Millie ranked 655th in popularity for females of all ages in a sample of the 1990 US Census.
Though this name has fluctuated in use, it has been quietly present throughout the last century.
Mildred was one of the Old English names overwhelmed by the French names brought to the British Isles by the Norman Conquest of 1066. For reasons unknown to scholars, it quietly re-emerged in the 17th century, then enjoyed a real heyday at the beginning of the 20th.
The 1945 film noire classic Mildred Pierce was nominated for six Academy Awards, and its star, Joan Crawford, won the award for Best Actress. It is probable that this movie contributed to Mildred's lastest burst of popularity (it has faded radically since), though its tortured tale of love and betrayal is difficult to associate with a baby girl.