The oldest or first-born among a group, especially the oldest child in a family.
From Old English 'eldesta,' the superlative form of 'eld' (old age). It uses the ancient superlative suffix '-est' to show the extreme degree of age within a group.
The word 'eldest' is interesting because English keeps it as a special word for family age relationships—we say 'oldest' for things but 'eldest' for people and especially children, preserving an older, more formal way of speaking about family hierarchy.
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