In royal houses the privy chamber seems to have started as a room between the great chamber, where the king was still sleeping, and his privy. It was probably the room in which he prepared himself for the privy. Privy and privy chamber were in charge of a minor official known as the groom of the stool or stole; the great chamber was under a much more important officer called the chamberlain. When the royal bed was moved out of the great chamber into the next room, the room was still called the privy chamber and was still in charge of the groom of the stole. In the later sixteenth and seventeenth centuries, as part of the constant series of retreats that make up the history of palace planning, the bed was removed from the privy chamber as well. It became a private dining and reception room, with a suite of private chambers beyond it, all collectively known as the privy lodgings. The groom of the stole remained in charge of the whole sequence; an official whose original job had been to clean out the royal latrines had become one of the most powerful and confidential of royal servants.
Mark Girouard, Life in the English Country House (57-58)