The Collaborative International Dictionary of English v.0.48:

Lagging \Lag"ging\, n.
   1. (Mach.) The clothing (esp., an outer, wooden covering), as
      of a steam cylinder, applied to prevent the radiation of
      heat; a covering of lags; -- called also deading and
      cleading.
      [1913 Webster]

   2. Lags, collectively; narrow planks extending from one rib
      to another in the centering of arches.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Cleading \Clead"ing\, n. [Scot., clothing. See Cloth.]
   [1913 Webster]
   1. A jacket or outer covering of wood, etc., to prevent
      radiation of heat, as from the boiler, cylinder. etc., of
      a steam engine.
      [1913 Webster]

   2. The planking or boarding of a shaft, cofferdam, etc.
      [1913 Webster]