The chronicle Nern Feveren, the "Tales of Feveren", records both excerpts of Feveren's personal journal and the ongoing story of his adventures in LotRO Middle-earth. However, occasionally the continuity of these tales is interrupted by stories that recall the young Green-elf's childhood in Eryn Milbar, the greenwood of Harlindon. Nern i Chîn Eryn Milbar is merely a collection of those interregna, curated for convenience.

   "The Eldar grew in bodily form slower than Men, but in mind more swiftly. They learned to speak before they were one year old; and in the same time they learned to walk and to dance, for their wills came soon to the mastery of their bodies. Nonetheless there was less difference between the two Kindreds, Elves and Men, in early youth; and a man who watched elf-children at play might well have believed that they were the children of Men, of some fair and happy people. For in their early days elf-children delighted still in the world about them, and the fire of their spirit had not consumed them, and the burden of memory was still light upon them.

   "This same watcher might indeed have wondered at the small limbs and stature of these children, judging their age by their skill in words and grace in motion. For at the end of the third year mortal children began to outstrip the Elves, hastening on to a full stature while the Elves lingered in the first spring of childhood. Children of Men might reach their full height while Eldar of the same age were still in body like to mortals of no more than seven years. Not until the fiftieth year did the Eldar attain the stature and shape in which their lives would afterwards endure, and for some a hundred years would pass before they were full-grown."
      - Morgoth's Ring, 'The Laws and Customs Among the Eldar'

In his essay, Quendi and Eldar, JRRT wrote, “S has hên, pl. hîn, mostly used as a prefix in patronymics or metronymics: as Hîn Húrin 'The Children of Húrin'.” Therefore the title of this chronicle is most likely very sloppy Sindarin; then again, woodland elves are not renowned linguists!

"... little is now known of the Silvan Elvish. The Silvan Elves had invented no forms of writing, and those who learned this art from the Sindar wrote in Sindarin as well as they could."
      - Unfinished Tales of Numenor and Middle-earth, "Appendix A, The Silvan Elves and Their Speech"

Etymology:

S. narn - “tale", (pl.) nern
S. hên n. “child”, (pl) hîn

Concerning Age in Relation to Appearance

Cirth transcription courtesy of Glǽmscribe