Mine is pretty simple to figure out...
Youngest of 7 kids and have always been called little sis or little sister since I can remember. I was little sis to all my siblings friends too.
Seemed like Lisa was a name that only came up when one of them was mad at me and that wasn't often, because I was such a sweet kid!!
I have used the name for everything, even on my license plate.
Thanks for bringing this question up again...great to see why people are who they are.