A Troglodyte

1. A member of a supposed prehistoric race that lived in caves or holes, a caveman.
2. (by extension) Anything that lives underground.
3. A reclusive, reactionary or out-of-date person, especially if brutish.
4. The Eurasian wren, Troglodytes troglodytes.
5. (computing) A person who chooses not to keep up-to-date with the latest software and hardware.