Are You My Sissy?

2 year old Z can say all of our names except for M.  Instead she calls her "sissy".
This morning we were going through everyone's names.
I asked Z, "Where's L? Can you say L?"
"Where's M? Can you say M"
And she says "sissy"
She also calls my mom, Grandma M, "sissy".  So I mentioned  that to her.
Then she says "L sissy"
"Me sissy"
"Momma sissy"
All in her cuteness.