My mother would hold her her firstborn grandchild (my daughter) and ask over and over, "What's my name?". When the baby finally responded she said what sounded like "Manny" (most likely trying to repeat "my name"). And so it stuck and the rest of the grandchildren were predestined to have a Manny.
My grandmother was "Mimi" (as decided by my brother, her first grandchild). I'm hoping to be called Mimi, too, but one never knows what that first grand baby will decide.