Ideas:

1. I have a suspicion that this type of sign (which certainly is similar to its equivalent in Hb9-55) shows two holes in what otherwise would be this type of sign:

2. Perhaps this is a way to describe the two holes through which the sun moves when entering and leaving this world of ours (te ao nei).

The ancient Egyptians believed in this too, that there must be holes through which the heavenly bodies moved into and out of our presence.

The Polynesian trickster Maui tried to follow in the wake of the sun in order to reach immortality. The sun returns each morning form the dark underside of the earth and never dies, because he is rejuvenated there.