Its source is Emma, an Ancient Germanic name meaning "Universal."
The name Emmett ranked 712th in popularity for males of all ages in a sample of 2000-2003 Social Security Administration statistics and 496th in popularity for males 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.
This surname evolved from a pet form of the female personal name. Compare this to Madison, derived from a pet form of Madeline, and Allison, derived from Alice.