Why is the ninth month called September?
c.1400, "full of caverns," from Latin cavernosus "full of cavities" (source also of Italian cavernoso, French caverneux), from caverna (see cavern). Meaning "hollow" is recorded from 1830.
cavernous cav·ern·ous (kāv'ər-nəs)adj. Filled with cavities or hollow areas; porous.