Old High Vulcan was an ancient language upon which modern Vulcan and Romulan languages were based. (TOS novel: The Romulan Way)
History and specifics[]
David Rabin spoke the traditional Vulcan greeting in Old High Vulcan when he was introduced to Ambassador Sarek on Vulcan in 2247. In Federation Standard, the greeting translates to "We come to serve," and the response is rendered as "Your service honors us." (TOS novel: Vulcan's Forge)