“Is there another usage of dhātu?”
Yes. Words can have different meanings depending on context.
That is true not only in Pali but in many languages. Following are some examples:
I left my phone on the left side of the room.
The baseball pitcher asked for a pitcher of water.
The committee chair sat in the center chair.
The crane (a bird) flew above the construction crane.
She will park the car so we can walk in the park.