In Sibbe Gerest, the Old English spell from Diamond of the Day, means more than simply “Rest in Peace.” Sibbe has a variety of meanings, including one for kinship or familial relationships. Our modern word sibling descends from this. It can also mean “natural affection,” “love,” or “friendship.” Peace is actually one of the least commonly used meanings of this word. There are many other ways of saying peace in Old English, and one that might be most applicable to our modern way of saying Rest in Peace would be frið, which carries with it the connotation of stillness or tranquility. Sibbe, however, is used by Bede in his Ecclesiastical History and in Layamon’s Brut to refer to the peace that comes after war, when two sides have finally reconciled. The Old English verb sibbian actually means to reconcile. When Merlin is telling Arthur to rest in peace, he is not just saying “Have a tranquil thousand years or so,” he is telling him that the time of battle is finally over. That he will go on to a place with no more war, no more concerns for Camelot’s safety. The connotations of love and family associated with sibbe are also present in his words to Arthur.
This is not just a request to Arthur. This is a command, a spell even. Merlin says, “In sibbe gereste.” He specifically says gereste (coming from gerestan). A similar verb exists in Old English: restan. By adding the “ge-” in front of the main verb, the meaning is exaggerated (for example, Biblical quotes will often use “ge-” verbs to demonstrate the importance of a specific moment). Both verbs mean “to rest, remain, or repose;” however, gerestian carries with it a sense of greater importance. Arthur is not only commanded, enspelled, into resting in peace after long battles, but Merlin wishes to emphasize that he will remain there. That this death, while not permanent, seems so to Merlin.