Intestines, from the Latin intestina, guts, which is from intus, within. The singular form, intestinus, means internal, domestic, or civil, and was a term used in governmental discourse by the ancient Romans.

The word clandestine (concealed, working in secret) comes from intestinus plus clam, Latin for secret

Intestina, in the anatomical sense, first appeared in a work by the great Roman anatomist Celsus in the first century B.C. (his book, De Medicina, was one of the first medical texts to be printed following the invention of the printing press 1500 years later).

Celsus also was the first to employ acetabulum and patella, among many other words of anatomy.

Aurelius Cornelius Celsus 53 B.C. - 7 A.D calder.med.miami.edu