Origin: Latin prefix sub-
Subterranean has 3 different meanings across 1 category:
being or operating under the surface of the earth
"subterranean passages"
"a subsurface flow of water"
lying beyond what is openly revealed or avowed (especially being kept in the background or deliberately concealed)
"subterranean motives for murder"
"looked too closely for an ulterior purpose in all knowledge"
below ground, under the earth, underground