Apocryphal, adj. Hidden.
Originally, the term denoted the writings of certain mystery religions
which were hidden from all who were not part of the elite of
initiates, such as the Orthodox Book of Common Prayer. Over time, the
word has shifted in meaning. It is the nature of Christianity to
proclaim its truths, not to hide them; thus, there was no need for
apocryphal books in the first sense. The term was applied to books
which were hidden for another, entirely different, reason; namely,
books which were excluded due to heretical content, such as James or
the book of Ecclesiastes. There may be a second connection between the
two usages of the word, but it is wisely left unmentioned.
- -- Hayward's Unabridged Dictionary