Lexicon Technicum, author John Harris, published 1710
"Rodknights alias Radknights were anciently Servitors, which held their land by serving their Lord on horseback; or attending him in his progress or travels on the road."
"An exact and Particular Account of the way and manner of the Killing of Commissioner Cayley, by Madam Mackfarling", published 1715
Untriguingly, the examination into his death refers to "... Mary Liddell, Servitor to John Mackfarlane, Writer to the Signet ..." and goes on to refer to " ... Barbara Martine, Servant to John Mackfarlane, Writer to the Signet ...".
In some instances servitor simply means servant but in others it identifies a relationship much more than this but which cannot be strictly interpreted. I've considered "follower, attendant, companion" - whichever, there's no specific, single interpretation.