Emily Dickinson Lexicon

ELD'EST, a. [Sax. ealdest, superlative of eld, old.]

Oldest; most advanced in age; that was born before others; as, the eldest son or daughter. It seems to be always applies 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.