Etymology
From Middle English tortuse, tortuce, tortuge, from Medieval Latin tortuca, of uncertain origin. May be from Late Latin tartarūcha, from tartarūchus, from Ancient Greek ταρταροῦχος (tartaroûkhos, “holder of Tartaros, Tartarus, the land of the dead in ancient stories”), because it used to be thought that tortoises and turtles came from the underworld and they were commonly paired with such infernal beasts; see Τάρταρος (Tártaros). Or, from Latin tortus (“twisted”). The French-looking Modern English spelling tortoise may be influenced by porpoise. Displaced native Old English byrdling.