The Collaborative International Dictionary of English v.0.48:

Lath \Lath\, n.; pl. Laths. [OE. laththe, latthe, latte, AS.
   l[ae]tta; akin to D. lat, G. latte, OHG. latta; cf. W. llath
   a rod, staff, yard. Cf. Lattice, Latten.]
   A thin, narrow strip of wood, nailed to the rafters, studs,
   or floor beams of a building, for the purpose of supporting
   the tiles, plastering, etc. A corrugated metallic strip or
   plate is sometimes used.
   [1913 Webster]

   Lath brick, a long, slender brick, used in making the floor
      on which malt is placed in the drying kiln.

   Lath nail a slender nail for fastening laths.
      [1913 Webster]