The Collaborative International Dictionary of English v.0.48:

Jackman \Jack"man\, n.; pl. Jackmen.
   [1913 Webster]
   1. One wearing a jack; a horse soldier; a retainer. See 3d
      Jack, n.
      [1913 Webster]

            Christie . . . the laird's chief jackman. --Sir W.
                                                  Scott.
      [1913 Webster]

   2. A cream cheese. [Obs.] --Sir T. Elyot.
      [1913 Webster] Jack-o'-lantern