Meaning

adjective being or suggesting a cavern

adjective filled with vascular sinuses and capable of becoming distended and rigid as the result of being filled with blood

originLate Middle English cavernous, cavernose, borrowing from Old French caverneux or Latin cavernōsus (“full of hollows or cavities”), from caverna (“a hollow, cavity, cave”) + -ōsus (“-ous, -ose”, adjectival suffix); equivalent to cavern + -ous.

Etymology from Wiktionary, CC BY-SA 3.0