troglodyte TROG-luh-dyt, noun:

1. A member of a primitive people that lived in caves, dens, or holes; a cave dweller.
2. One who is regarded as reclusive, reactionary, out of date, or brutish.

Troglodyte comes from Latin Troglodytae, a people said to be cave dwellers, from Greek Troglodytai, from trogle, “a hole” + dyein, “to enter.” The adjective form is troglodytic.

I know it’s not as uncommon as some of the words, but I really like it.