The noun ᴱQ. qilde or qille “quiet, rest, hush” appeared in the Qenya Lexicon of the 1910s under the early root ᴱ√QḶÐḶ (QL/44). Qilde also appeared in the contemporaneous Gnomish Lexicon as equivalent to (deleted) G. clidhron (GL/23). The Declension of Nouns from the early 1930s instead had noun ᴹQ. qilir “quiet” derived from primitive ᴹ✶ku̯ilẹz (PE21/33-34), based on a similar root.
Neo-Quenya: For purposes of Neo-Quenya, I prefer ᴺQ. quildë “quiet, rest, hush” as most compatible with its adjective form ᴺQ. quilda “quiet, hushed, still” and the later Quenya syncope.
The correlative ᴹQ. iro appeared in Demonstrative, Relative, and Correlative Stems (DRC) from 1948 (PE23/111), a combination of the relative pronoun ᴹQ. i and ᴹQ. -ro “reason”.
Neo-Quenya: For purposes of Neo-Quenya I would update this to ᴺQ. yaro “for the same reason as” using the relative pronoun ya more commonly used in declined forms in later writings, such as Q. yassë “where [relative]”. For example: nilin Quenya yaro lye “I love Quenya for the same reason as you”. Hat-tip to Vyacheslav Stepanov for suggesting this gloss; compare ᴹQ. inárea “as old as” and Q. yallë “in the same way as”.