Word Class: 
Even though, despite. This particle occurs at the beginning of a clause, setting up some proposition, which is then contradicted. This could be explicated as 'Even though X would lead you to assume Y, actually Z is the case'. Ninggi introduces proposition X.
Kurungurr Example:
Ninggi mani yaringngi fime, minbe ngaganim.
Even though you gave me the money (to go), I'm not going.
Kurungurr Example:
Ninggi tyawurru dam fisul, ep nginimem bulbulfi.
Even though the sun's only just up, it's already hot.