The Colour of Magic

39

In Greek mythology Tethys or Thetis was the personification of the feminine fecundity of the sea. She was the daughter of Uranus and Gaia, and the youngest female Titan (or Titanide). Eventually she married her brother Oceanus, and together they had more than 3000 children, namely all the rivers of the world.

Undoubtedly because of these origins, ‘Tethys’ is a name that has been given to, amongst others, a tropical sea that existed during the Triassic era in what is now Southern Europe, and to a moon of Saturn, one primarily composed of water ice.

Note that this is one instance where it appears Terry violates his own unwritten rule that trolls should have ‘mineral’ names. Perhaps this is simply because we are looking at this early book in the series with hindsight: the only rock troll to appear up to this point lasted about three paragraphs and didn’t have a chance to introduce himself. But even if the unwritten rule was already established in Terry’s mind at this point, it seems reasonable that it need not apply to Tethis, who is, after all, neither a rock troll nor originally a Discworld creature.