A word given as {cwanca- >>} G. cwancha- “to ail” in the Gnomish Lexicon of the 1910s, verb form of G. cwanc “sickly” (GL/28).
Neo-Sindarin: For purposes of Neo-Sindarin I would update this word to pavra- “to ail, be ill”, based on the later word [N.] paw “sickness” and its root ᴹ√KWAM (Ety/KWAM).
An adjective in the Gnomish Lexicon of the 1910s glossed “sickly, poorly, seedy”, based on the early root ᴱ√QAMA like other related words (GL/28).