1382, "a roofing slate," from O.Fr. esclat "split piece, splinter," back-formation from esclater "to break, splinter, burst," probably from Frank. *slaitan "to tear, slit," related to O.H.G. slizan, O.E. slitan (see slit). Meaning "long, thin, narrow piece of wood or metal" attested from 1764.