Sacred or Secret?
Devoted or dedicated to a deity or to some religious purpose; consecrated, reverently dedicated to some person, purpose or object.
Sacred – Webster’s 1828 Dictionary
Holy, pertaining to God or to his worship; separated from common secular uses and consecrated to God and his service as a sacred place, a sacred day, a sacred feast, sacred service, sacred orders.
Done, made or conducted without the knowledge of others, kept from the knowledge of any but the initiated or privileged, secluded, sheltered or withdrawn.
Secret – Webster’s 1828 Dictionary
A thing not discovered and therefore unknown.