A verb appearing as G. {irta- >>} irtha- “peck” in the Gnomish Lexicon of the 1910s (GL/52), probably based on the early root ᴱ√ᴵRTYᴵR “peck, prick” from the contemporaneous Qenya Lexicon (QL/43).
Neo-Sindarin: I would retain this verb as ᴺS. irtha- “to peck” based on the Neo-Root ᴺ√IRIT “peck, prick”.
A noun appearing as G. irt⁽⁾ “beak (of small birds)” in the Gnomish Lexicon of the 1910s (GL/52), clearly based on the early root ᴱ√ᴵRTYᴵR “peck, prick” (QL/43). There was no irt⁽¹⁾.
Neo-Sindarin: For purposes of Neo-Sindarin, I would adapt this word as ᴺS. irth “beak” based on the Neo-Root ᴺ√IRIT; compare S. amarth < ✶(a)mbarta.