I know what Emmett Till's mother's name was ...
And I also know that Mamie Van Doren and Mamie Eisenhower were both white. That doesn't change what I said.
It's not an explicit racial connotation like Mammy; it's closer to Jemima, or Hattie or Mattie. The Frog Princess was originally going to be called Mattie but Disney changed it to Tiana because Mattie is seen, by many Black people, as a "slave name." I didn't want to call Mamie a "slave name" but that's what lots of people who would know better than I do and certainly better than you do consider it.
Before you criticize a man, walk a mile in his shoes. That way, when you criticize him, you're a mile away and you have his shoes!
Steve Martin