2. A private chamber; a sanctum: "During the court adjournment, the judge went to his adytum for a little rest."
3. Etymology: from Greek a-, "not" plus Greek dyein, "to enter".
Some historical background information regarding adyta
A secret chamber or place of retirement in the ancient temples, and considered to be the most sacred spot, the innermost sanctuary, or shrine. No one but the officiating priests were permitted to enter and from which the oracles were given.
The Holy of Holies, or Sanctum Sanctorum, of the temple of Solomon was of the nature of the pagan adytum; none but the high priest was only one allowed into it, and he could go there just once a year.
Among the Egyptians the secos was the same thing, and it is described by Strabo. A well-preserved adytum that has come to our knowledge is in the little temple in Pompeii; it was raised some steps above the level of the temple itself, and it was without light.
With reference to Christian architecture, it sometimes signifies the chancel, or the altar end of a church.