eldest

The word "eldest" is a direct descendant from Old English 'ieldest', the superlative form of 'eald' (old). Its core morpheme, "eld," is a fossilized comparative form that has survived primarily in this specific construction. The addition of the superlative suffix "-est" creates a word that specifically denotes the most senior by age among a group. While the simpler root "old" (from Proto-Germanic aldaz) became standard, "eldest" was preserved in English to serve this precise, relational function within families or sets, illustrating how a grammatical form can lexicalize into a fixed adjective.

Structure: eld (old) + est (superlative suffix) - eld: From Old English 'ieldra' (older), related to 'eald' (old). It functions as the comparative root meaning "older." - est: A superlative suffix from Old English '-est', '-ost', used to form the highest degree of comparison.