Roucebourc
In Guillaume le Clerc’s Fergus, a castle in Lothian, where Lady Galiene of Lothian was besieged by a malicious king. Arondele, Galiene’s maidservant, went out to find a champion, and found the absent knight Sir Fergus.
Guillaume was probably reffering to the actual Scottish castle of Roxburgh.
Source
Fergus | Guillaume le Clerc, 1200-1233