hamadryad (n.)

late 14c., from Greek hamadryas (plural hamadryades) "wood-nymph," fabled to die with her tree, from hama "together with" (from PIE root *sem- (1) "one; as one, together with") + dryas (plural dryades) "wood nymph," from drus (genitive dryos) "tree," especially "oak," from PIE root *deru- "be firm, solid, steadfast," with specialized senses "wood, tree." Use in 19c. biology for a type of butterfly, a type of venomous Indian serpent, and a type of large hairy baboon.