late 14c., neuter plural of Late Latin apocryphus "secret, not approved for public reading," from Greek apokryphos "hidden; obscure," thus "(books) of unknown authorship" (especially those included in the Septuagint and Vulgate but not originally written in Hebrew and not counted as genuine by the Jews), from apo- "away" (see apo-) + kryptein "to hide" (see crypt). Properly plural (the single would be Apocryphon or apocryphum), but commonly treated as a collective singular.
1. Although New Testament apocrypha go into these details, some quite extensively.
2. Esdras is the first two books of the old testament apocrypha.