It comes from the Giants that got it from the Elohim, but then a few chapters later in the one Tree we learn from the Elohim themselves that they don't really use the term but use "Wurd".
And the Waynhim and Demondim speak of "Weird""Sun-Sage," replied Daphin, "we are the Wurd of the Earth."
She spoke clearly, but her tone was confusing. Her Wurd sounded like Wyrd or Word.
Wyrd? Linden thought. Destiny-doom? Or Word?
Or both.
Into the silence, Daphin placed her story. It was an account of the creation of the Earth; and Linden soon realized that it was the same tale Pitchwife had told her during the calling of the Nicor. Yet it contained one baffling difference. Daphin did not speak of a Worm. Rather, she used that blurred sound, Wurd, which seemed to signify both Wyrd and Word.
It's not the whole of the earth in size but rather a range of hills.
We really have no concept of what this thing is.