The Collaborative International Dictionary
Lath nail
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.
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.
Wiktionary
lath nail
n. A slender nail for fastening laths.