- index
- late 14c., "the forefinger," from L. index (gen. indicis) "forefinger, pointer, sign, list," lit. "anything which points out," from indicare "point out" (see indicate). Meaning "list of a book's contents" is first attested 1570s, from L. phrases such as Index Nominum "Index of Names," index expurgatorius "specification of passages to be deleted from works otherwise permitted." The verb meaning "compile an index" is from 1720. Scientific sense (refractive index, etc.) is from 1829; economic sense (cost-of-living index, etc.) is after 1886. The Church sense of "forbidden books" is from index librorum prohibitorum, first published 1564 by authority of Pius IV.