The "Pieces of Me" singer has a 6-year-old son with her ex-husband, Fall Out Boy bassist Pete Wentz. Seeing as their boy's name is Bronx Mowgli, Simpson's new daughter clearly needed an equally unique name. Wentz also welcomed a second child, son Saint Lazslo, in August 2014 with girlfriend Meagan Camper. Hollywood names abound for these musical families!
It's pretty safe to say that the unique moniker for the newest member of the Simpson-Ross clan pays homage to that famous Rolling Stone, Mick. Jagger has an English origin and is usually bestowed upon boys, though actress Soleil Moon Frye also gave her now 7-year-old daughter the same moniker when she was born in 2008.