Earlier form of S. Iarwain appearing in Lord of the Rings drafts from the 1940s, translated “Eldest” and appearing beside N. Iaur (TI/125). It might be a superlative form of iaur “old”; in the Early Noldorin Grammar, the similar suffix -iant was used for the superlative (PE13/125). If the suffix -ion was a Noldorin superlative suffix, perhaps the initial [e] developed due to Noldorin i-affection.
Noldorin
forn
adjective. right or north
forn
noun. right, north
forn(en)
adjective. closed
forven
noun. north
forven
noun. north
fenn forn(en)
place name. Closed Door
erion
masculine name. Eldest
feir
noun. right (hand)
forgam
adjective. right-handed
forod
noun. north
forod
noun. north
fœir
noun. right (hand)
iaur
masculine name. Eldest
uidavnen
adjective. ever-closed
Normalized to uidafnen, as in lefnui
Earlier name for S. Fen Hollen in Lord of the Rings drafts from the 1940s glossed “Closed Door” (WR/338, 341), a combination of fenn “door” and forn(en) “closed”.