They came forth from the uanga (maggots, fruitfly larvae; apparently also in Tonga seen as a source of generatio spontanea). Their being-first status has elevated them from mere mortals into the realm of divinity, and added mystical significance to their names.
These creatures originated from the uanga (maggots, fruit fly larvae; they are also believed to be a source of spontaneous generation in Tonga).  Their position as the first life forms has made them divine beings, and their names have acquired mystical importance.