- subterranean (adj.)
- c. 1600, from Latin subterraneus "underground," from sub "under" (see sub-) + terra "earth, the ground" (see terrain) + -an.
- subterraneal
- "Underground; = subterranean", Late 16th cent.; earliest use found in Robert Dallington (b. 1561), author and courtier. From classical Latin subterrāneus + -al.