The term 'Tortoise Foe' is a reference to the classic Aesop's fable, 'The Tortoise and the HARE'. In the story, the HARE is the tortoise's foe, as it is the HARE who challenges the tortoise to a race. The HARE is confident that he will win, but the tortoise ultimately wins the race due to his slow and steady pace. The HARE is thus the tortoise's foe in the story, and can be represented by the four letter word 'HARE'.