Ideas:

Although Metoro is saying maunga about half the times, when seeing this type of glyph while reading Tahua, there is also a significant frequency of heke (= octopus) instead.

I think this is because Metoro had a third way of explaining the essence of meaning behind this type of glyph. In addition to kana rei, something hidden inside the hair, and maunga, which perhaps is a shortened expression for 'hide in the mountains', the behaviour of an octopus should also make the meaning clear.

When an octopus notices an enemy (like man) he quickly hides in a rocky crevice.