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!
porog
noun. fowl (domestic)
porogwil
noun. hen
The word G. porogwil appeared in the Gnomish Lexicon of the 1910s as a combination of G. porog “fowl (domestic)” and G. uil “hen” (GL/64, 74).
Neo-Sindarin: I would adapt this word as ᴺS. porochuil for purposes of Neo-Sindarin, updating the second element to the neologism ᴺS. huil “hen”. The longer form is better distinguished from ᴺS. huil “bitch, female dog”.
porogog
noun. the clucking and noise of fowls
uil
noun. hen
The word G. uil “hen” appeared in the Gnomish Lexicon of the 1910s (GL/74), almost certainly a cognate of ᴱQ. oi “bird, hen” which Tolkien considered deriving from ᴱ√OHO “cry” (QL/69). In Common Eldarin: Noun Structure from the early 1950s, Tolkien had the primitive word ✶kholjē “hen” derived from the root √KHOL “crow, cry aloud” (PE21/82), which may be a later iteration of this Gnomish uil “hen” word.
Neo-Sindarin: Based on the above, Gábor Lőrinczi proposed a neologism ᴺS. hŷl “hen” as recorded in the VQP (VQP). However, my analysis of Sindarin phonology indicates that ᴺS. huil is the more likely result ✶kholjē: compare thuil and thuin plurals of thôn and thôl, and possibly also ruin < ✱runyā and fuir < ✱forya. For further details see the entry on how [[s|final [i] intruded into preceding syllable]] in Sindarin.
In any case, I recommend ᴺS. huil for “hen” in Neo-Sindarin, or its more elaborate form ᴺS. porochuil.
The word G. porog “fowl (domestic)” appeared in the Gnomish Lexicon of the 1910s (GL/64), clearly the cognate of ᴱQ. poroke “barn fowl” from the contemporaneous Qenya Lexicon (QL/75). In Common Eldarin: Noun Structure from the early 1950s, Tolkien had primitive words ✶porokĭ “fowl” and ✶porokē “hen” (PE21/82), indicating this Gnomish word may have remained valid in later Sindarin.
Neo-Sindarin: Gábor Lőrinczi proposed a neologism ᴺS. prôg “fowl, hen” as recorded in the VQP (VQP), but I personally would just stick with attested ᴺS. porog, derived from ✱pórŏkē. Furthermore, I’d limit this word to just “fowl” or “✱chicken”, and recommend ᴺS. huil or ᴺS. porochuil for “hen”.