A medieval drawing of an amphisbaena.
A curious beast, to be sure, and possibly an inspiration for Dr. Dolittle's Pushmi-Pullyu. For certain, it has given its name to a genus of New World lizards with heads that look similar to their tails. In mythology, they are said to have been created from the blood dripping from Medusa's head as Perseus carried it over the Libyan desert. Most curious to me is that it has some connection with ants: Pliny the Elder claimed that they ate ants, while some sources give it the epithet Mother of Ants. Adopted in English in the 14th century from Latin, ultimately from Greek, from amphís, both ways + baínein, to go.