Orthogonalities are something that I've been working on recently, and saw Rancticirchiretic as an excellent opportunity to unfurl. One of my primary problems with Ghyll, that no one else seems to have noticed, is its discrepancy in size: it's way too small, by historical accident in the mapmaking process. Orthogonalities provide a way to expand the area without changing the map, without changing the makeup of the encyclopaedia, and whilst being consistent with many other points. For example, it's easy to start to explain Cartographer's Nerves (or make it more obfuscationary), and it explains why we need Pachyderm courier services even though the world is so small, and why entries to the encyclopaedia get in in poor conditions, and so on.
I think it's consistent with being "discovered" by Rancticirchiretic in much the same way that gravity was discovered by Newton. It's always been there for the inhabitants of Ghyll, but not given a name or understood.
One of the main things to realise about them is that in the centre of the Ghyll map they're very orderly and easy to travel between, whereas as you get towards the edges they become rather messy and maze-like, which is why people tend to avoid the edges, and which is why Ghyll, or rather the primary orthogonality, is so small.