"Morlock" is a term primarily known for being used in H.G. Wells' novel, "The Time Machine". It refers to a fictional species of nocturnal, subterranean creatures that coexist alongside the Eloi. However, since it is a unique concept, there are no direct synonyms for this specific word. To explore alternative terms that somewhat resemble the characteristics of a Morlock, one might consider words such as "subterranean dwellers", "cavern inhabitants" or "underground species". While these options convey a similar concept of creatures living in hidden places, they do not encompass the exact essence and attributes of a Morlock as imagined in Wells' work.