Eldest
Easton’s Bible Dictionary & Webster’s 1828 Dictionary · Matthew George Easton, Noah Webster
Eldest - (Webster's 1828 Dictionary)
ELD'EST, a. Oldest; most advanced in age; that was born before others; as the eldest son or daughter. It seems to always applied to persons or at least to animals, and not to things. If ever applied to things, it must signify, that was first formed or produced, that has existed the longest time. But applied to things we use oldest.
Source of the article
Matthew George Easton, Easton’s Bible Dictionary; Noah Webster, American Dictionary of the English Language (1828)
Bible Strong combined digital edition