The Collaborative International Dictionary of English v.0.48:

Sheading \Shead"ing\, n. [From AS. sc[=a]dan, sce['a]dan, to
   separate, divide. See Shed, v. t.]
   A tithing, or division, in the Isle of Man, in which there is
   a coroner, or chief constable. The island is divided into six
   sheadings.
   [1913 Webster]