It's an affectionate term for grandmother (one that a child might use).
Großmutter, or more familiarly, Oma, Omama Omi
omi
Oma Omi
Nana = Oma Nana = Omi
grandmother = Großmutter grandma = Oma, Omi, Omilein, Omchen
Nana = Oma Nana = Omi
It doesn't mean anything in Japanese. I know because Omi is my name, and I've thoroughly looked into it ;)
there is no such word in German
ALL or EVERY
it means: samoan/mexican((:
greave is not a German word.
But isn't a German word.