Early Quenya
filqe
noun. fern
filinqe
noun. fern
filimpe
noun. fern
Beware, older languages below! The languages below were invented during Tolkien's earlier period and should be used with caution. Remember to never, ever mix words from different languages!
A word appearing as ᴱQ. filqe “fern” in the Qenya Lexicon and Poetic and Mythological Words of Eldarissa of the 1910s, with variants filinqe and (dialectical) filimpe [probably Solosimpi/Telerin], all derived from the early root ᴱ√FILI “fine, thin” (QL/38).
Conceptual Development: The Declension of Nouns (DN) of the early 1930s had ᴹQ. filet (filek-) with glosses {“fern” >>} “cobweb” (PE21/33 note #123), and in later writings filit (filik-) was a word for “small bird, sparrow” (Ety/PHILIK; PE21/56).
Neo-Quenya: Since there are no later non-rejected words with this meaning, I would retain ᴺQ. filquë “fern” for purposes of Neo-Quenya.