Well, here's what I think.
The World Knots are demonstrably quite fragile. A few satchels and they're destroyed. So they can't be *that* old or they'd be gone by now. They can be repaired, of course, but if they were many millennia old, the mechanisms would have been damaged irreparably, or vital chunks would have been lost. So I don't think they're holdovers from the Elder World.
Why were they built near the lands of the Trow? First, I doubt they were actually created by the Trow--the architectural style is wrong, as well as the scale itself. And the majority of the knots are (insofar as we know) in human/Dwarf-populated lands, rather than those regions which Trow have historically frequented. Although this might just be because we've only heard about the Knots humans are interested.
But if they're non-Trow, why would they dare to establish a World Knot near the Trow capital, and how did they manage it without being attacked? Well, there's one time when anyone could have walked up there and built whatever they wanted without fear, and that's in the period after Connacht imprisoned the Trow but before Balor released them. The early part of which, coincidentally, is when the Smiths of Muirthemne were active.
Another point: Apparently the Dark didn't know how to operate the World Knots until midway through TFL. That's what The Head said, and for once he appeared not to be lying. But why would the Nine know how to use them, if the Fallen Lords didn't? After all, at least a few of the Fallen Lords--such as Balor and Myrdred--were once powerful Light magicians.
The only conclusion possible, it seems to me, is that *nobody* (except for their makers) figured out how to use the World Knots until after Connacht and Myrdred both disappeared into the East, prior to returning as Dark lords. And this, again, suggests that the World Knots were made relatively recently--so recently that even the Light's last great champion had no time to figure out how to use them before he left.
So, to summarize--the Smiths built the World Knots around or just after the time of Connacht's great wars; in particular, they established the Rhi'anon World Knot shortly after the defeat of the Trow. The Smiths were driven into the Tain; Connacht and Damas, and then Myrdred, left for the East; and at some point after that, the Nine worked out how the Smiths had used the Knots. Then, when the Dark came back, it took them a few years to figure it out for themselves.
And that's my opinion.
--SiliconDream
