In German, name Millie means – Strength, determination. Diminutive of Amelia: From the Old German Amalburga, meaning labour, and the Latin Aemilia. Famous bearers: 18th century British King George IIIs daughter Princess Amelia Henry Fieldings novel Amelia.. Other origins for name Millie include – German, American, English, French. Name Millie is most often used as a girl name or female name.