Mid 17th century. Perhaps shortened from subterranean, or perhaps from sub- + classical Latin terreus made of earth, sprung from earth, consisting of earth + -an.
Definition of subterrean in US English:
subterrean
adjectivesʌbtəˈrɪən
Underground; = "subterranean".
Origin
Mid 17th century. Perhaps shortened from subterranean, or perhaps from sub- + classical Latin terreus made of earth, sprung from earth, consisting of earth + -an.