Quenya 

felco

noun. cave, mine, underground dwelling

A word for “cave, mine, underground dwelling” Tolkien considered in Notes on Names (NN) from 1957, derived from the root √PHELEK as a possible replacement for felya “mine, boring, tunnel, underground dwel[ling]” < ✶phelgā (PE17/118).

Neo-Quenya: I prefer the root form √PHELEG over √PHELEK (see that entry for details) and as a result prefer felya over felco.

felco

cave, mine, underground dwelling

felco noun "cave, mine, underground dwelling" (PE17:118); also felca, felehta

felca

felca

felca, see felco

felehta

felehta

felehta, see felco

felya

cave

felya noun "cave" (PHÉLEG), "mine, boring, tunnel, underground dwel[ling]" (PE17:118)

rotelë

cave

rotelë noun "cave" (LT2:347)

rotto

cave, tunnel

rotto noun "cave, tunnel" (VT46:12), "a small grot or tunnel" (PM:365)