The first mention of Holyroodhouse is in: Chapter 1: The Palace.
"The Palace of Holyroodhouse, commonly referred to as Holyrood Palace, is the official residence of the monarch in Scotland. Holyrood Abbey was founded by David I, King of Scots in 1128, and Holyrood has served as the principal residence of the Kings and Queens of Scots since the 15th century. The Palace stands at the bottom of the Royal Mile in Edinburgh, the opposite end to Edinburgh Castle.
Queen Elizabeth II spends one week in residence at Holyrood at the beginning of each summer, to host garden parties and official ceremonies. She then continues to Balmoral Castle (which she owns) for her annual two-month summer holiday.
Holyrood is an anglicisation of the Scots Haly Ruid, meaning holy cross." Holyroodhouse, Wikipedia