Tortoise means animal of a sunless abyss

The word tortoise is quite a mystery.

Tortoise is a weird word. Tortoise. Tortoise. Just look at it. Tortoise. Tor-toise. It almost sounds dainty. But it's for a clunky turtle.

Etymonline.com doesn't reveal much:

1550s, altered (perhaps by influence of porpoise>) from Middle English tortuse> (late 15c.), tortuce> (mid-15c.), tortuge> (late 14c.), from M.L. tortuca> (mid-13c.), perhaps from L.L. tartaruchus> "of the underworld" (see turtle). Others propose a connection with L. tortus> "twisted," based on the shape of the feet. The classical Latin word was testudo>, from testa> "shell." First record of tortoise shell> as a coloring pattern is from 1782.

How about dictionary.com?

Origin:
1350–1400; variant of earlier (15th-century) tortuse, tortose, tortuce, Middle English tortuca < Medieval Latin tortūca, for Late Latin tartarūcha (feminine adj.) of Tartarus (< Greek tartaroûcha), the tortoise being regarded as an infernal animal; Medieval Latin form influenced by Latin tortus crooked, twisted

What is this Tartarus?
1. a sunless abyss, below Hades, in which Zeus imprisoned the Titans.
2. a place in Hades for the punishment of the wicked.

So basically the tortoise is the animal of a sunless abyss. Poor tortoise.