The Collaborative International Dictionary of English v.0.48:

Slade \Slade\, n. [AS. sl?d.]
   1. A little dell or valley; a flat piece of low, moist
      ground. [Obs.] --Drayton.
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   2. The sole of a plow.
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The Collaborative International Dictionary of English v.0.48:

Sole \Sole\ (s[=o]l), n. [AS. sole, fr. L. soolea (or rather an
   assumed L. sola), akin to solumround, soil, sole of the foot.
   Cf. Exile, Saloon, Soil earth, Sole the fish.]
   1. The bottom of the foot; hence, also, rarely, the foot
      itself.
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            The dove found no rest for the sole of her foot.
                                                  --Gen. viii.
                                                  9.
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            Hast wandered through the world now long a day,
            Yet ceasest not thy weary soles to lead. --Spenser.
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   2. The bottom of a shoe or boot, or the piece of leather
      which constitutes the bottom.
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            The "caliga" was a military shoe, with a very thick
            sole, tied above the instep.          --Arbuthnot.
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   3. The bottom or lower part of anything, or that on which
      anything rests in standing. Specifially:
      (a) (Agric.) The bottom of the body of a plow; -- called
          also slade; also, the bottom of a furrow.
      (b) (Far.) The horny substance under a horse's foot, which
          protects the more tender parts.
      (c) (Fort.) The bottom of an embrasure.
      (d) (Naut.) A piece of timber attached to the lower part
          of the rudder, to make it even with the false keel.
          --Totten.
      (e) (Mining) The seat or bottom of a mine; -- applied to
          horizontal veins or lodes.
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   Sole leather, thick, strong, used for making the soles of
      boots and shoes, and for other purposes.
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