Shining (like eyes, lamp); phosphorescent (as eyes of cats in the dark, and of some snakes); luminous.
There is a phosphorescent fungus called lamag. Possibly ngāmag is a frozen form originating from nga- plus lamag.
Ngāmag matanen.
His eyes are luminous.
Payamanun be lelipanin, ngāmg bang dem kalindeman.
Look at the centipede; it is phosphorescent in the dark.
Perhaps they are not yet asleep; their lamp is still shining.
That watch is luminous at night.