Christopher Tolkien has noted that Ilmen is related to such words as Ilmarë and Ilmarin.
Quenya
ilwen
feminine name. Ilwen
Elements
Word Gloss IL “all” vendë “maiden, *virgin”
ilmen
Ilmen
Yón
region, any (fairly extensive) region between obstacles such as rivers or mountains
yón (2), variant of yondë, q.v. Defined as "a region, any (fairly extensive) region _between obstacles such as rivers or mountains" (PE17:43)_
ména
region
ména noun "region" (MEN). Not to be confused with the present/continuative tense of #men- "go".
yón
noun. region
A possible wife of Q. Ingwë in some 1959 notes (NM/128).