What is "orthe"

Orthe is a series of science-fiction novels by Mary Gentle.

The Orthe series consists of the books Golden Witchbreed (published 1983) and Ancient Light (1987) and the short story The Crystal Sunlight, the Bright Air (1983). The action in both books takes place on a distant planet called Orthe, which is visited by Lynne de Lisle Christie, a British envoy from a not very far future Earth that has developed a spacefaring civilization.