[f. THUMB sb. + SCREW sb.; cf. Ger. daumschraube.]
1. A screw with a flattened or winged head, adapted for being turned with the thumb and fingers; a butterfly screw; also a small clamp adjusted by such a screw.
1794. Felton, Carriages (1801), Gloss., Thumb Nut or Screw.
1805. Dickson, Pract. Agric., I. Pl. xxiv. On the side of the tub is a thumb screw fixed to the lever underneath, which regulates the stones.
1888. Lockwood’s Dict. Mech. Engin., s.v. Screw Clamp, Small screw clamps are sometimes called thumb screws.
1908. Times, 22 April, 5/5. A thumb-screw securing the sashes had been removed.
2. An instrument of torture by which one or both thumbs were compressed; cf. THUMBIKINS; also called ‘the screws’ (SCREW sb.1 1 e).
[a. 1715. Burnet, Own Time, xvi. Little screws of steel were made use of, that screwed the thumbs [etc.: see SCREW sb.1 1 e].]
1817. Scott, Old Mort., xxxvi. An oaken table … on which lay thumb-screws, and an iron case, called the Scottish boot.
1832. G. Downes, Lett. Cont. Countries, I. 200. Such intellects as devised the rack and the thumb-screw.
1855. Macaulay, Hist. Eng., xiii. III. 290. The using of racks and thumbscrews for the purpose of forcing prisoners to accuse themselves.
1859. Jephson, Brittany, iii. 34. A grm functionary, whose countenance was suggestive of dungeons and thumbscrews.
