Meaning I'm in God's hands.
It's an ewe name in Togo.
Mau is God
Si is hand.
Mele Mausi means I'm in God's hands

To prove that it isn't difficult to make a word up and post it's definition online.

A Mausy is a girl, to be specific a girls sex organ :)
Used in Dublin as a slang for a girl you’d get with
Pronounced: mossy