1721, from Latin intestinum caecum "blind gut," from neuter of caecus "blind, hidden," from Proto-Italic *kaiko-, from PIE *kehi-ko- "one-eyed," cognate with Old Irish ca'ech "one-eyed," coeg "empty," Welsh coeg-dall, Old Cornish cuic "one-eyed;" Gothic haihs "one-eyed, blind." So called for being prolonged into a cul-de-sac.