The scientific name combines Greek elements meaning double and beam. It refers to double chevron bones associated with the tail vertebrae.
This is a modern scientific formation from Greek elements. The deeper derivation of dokos is qualified in the source and is not scored.
Sources
- Merriam-Webster: diplodocus
Word History supplies dokos and the anatomical naming explanation.
- Merriam-Webster: diplo-
Combining-form sense 1 gives double or twofold; Word History traces it to Greek.
- Online Etymology Dictionary: diplo-
Also built on Greek *diploos* "double" (diplo-): diploma, diplomatic
- Online Etymology Dictionary · diplodocus
Meanings of the older forms on the word path.