cavern
n.
late 14c., from Old French caverne (12c.) "cave, vault, cellar," from Late Latin caverna "cave," from Latin cavus "hollow" (see cave, n.). In Old English such a land feature might be called an eorðscræf.
〔李〕[cav;-ernn.] n.巨穴; 大洞 ←cav (L cavus)=hollow 凹陷