Thack

The said day, it was represented that the thacking and covering of Houses houses in the towne with straw and hedder wes very dangerous, and rendered them obnoxious to fyre, and to the endangering of the saids houses and the neighbouring adjacent houses, and that a fatall evidence thereof, by haveing some houses thacked and covered as said is, had falne out in the Gallowgate lately; […] .

This outer layer was generically known as 'thack', but, owing to the fact that the vast majority of buildings in early times were covered with a thacking of straw or some similar material, 'thatch' gradually acquired its modern restricted significance of straw, or reed, heling.

1860, Albany Fonblanque, Jun., Hector Mainwaring; or, A lease for lives, Ward and Lock, page 205, Thack ! thack ! thack ! the heavy hunting whip came down upon the head and shoulders of Charles Dudley.