The term Oldtimers has had a number of meanings in different eras of Pern's history.
In the Third Pass, it was used to refer to the original colonists. It is not clear how long this usage existed.
In the Ninth Pass, it originally referred to any Dragonrider who came forward in time from the Eighth Pass with Lessa. Later, the term came to refer specifically to those Oldtimers who refused to follow Benden's leadership, and were exiled to Southern Weyr. By analogy, when they began rediscovering their origins, the term "Ancienttimers" was used for the colonists.