Will 1860s-80s do OK?
OED:
Cosh (meaning no. 3):
A stout stick, bludgeon or truncheon; a length of metal used as a life-preserver; also (dial.), a stick; a school cane; a caning. Phr. under the cosh, at one's mercy, helpless.
1869 ‘A MERCHANT’ 6 Yrs. in Prisons vii. 76 The coshman (a man who carries a ‘cosh’ or life preserver). a1889 in Barrère & Leland Dict. Slang (1889) s.v., The officer..sought to give the finishing coup de grâce with his cosh. 1893 H. T. COZENS-HARDY Broad Norfolk 83 Words which I have been accustomed to hear in common use... Cosh,..a stick. 1896 A. MORRISON Child of Jago i, The cosh was a foot length of iron rod, with a knob at one end, and a hook (or a ring) at the other. 1898 WRIGHT Eng. Dial. Dict. s.v., Cosh, ..a caning at school. War[wickshire]. You will get the cosh. 1904 Daily Chron. 29 Sept. 4/5 ‘Coshes’pieces of lead pipe, known to the police as life-preservers. 1925 FRASER & GIBBONS Soldier & Sailor Words 64 Cosh, the bludgeon carried by night patrols men and trench raiders. Ibid. 138 Kosh, a name for a trench club, or knobkerry, used in trench raids. 1927 Weekly Dispatch 23 Oct. 4 A truncheon, or, in prison vernacular, ‘kosh’. 1958 F. NORMAN Bang to Rights I. 37 In the nick where you are under the cosh..most of the screws seem to take a sadistic delight in makeing [sic] things as uncomfortable as they can for you. 1959 ‘M. AINSWORTH’ Murder is Catching i. 19 Clench a newspaper over a handful of coins and you've got a comfortable little cosh. 1959 I. & P. OPIE Lore & Lang. Schoolchildren xvii. 374 Amongst children one of the most common names for the cane is ‘the cosh’. 1960 Observer 24 Jan. 7/2 As for the Criminal Justice Act, it could be very useful to have all the villains under the cosh, as they expressed it. It made it much easier to get information. 1965 Spectator 15 Jan. 67/1 All chains gone from the boys' lavatories to make coshes.
Blackjack (meaning no. 9):
A weapon consisting of a weighted head and short pliable shaft, used as a bludgeon. Hence as v., to strike with a blackjack. U.S.
1889 in Cent. Dict. 1895 Denver Times 5 Mar. 8/5 During the scuffle Miss Alderfer, Knapp's niece, saw the ‘black jack’ up his sleeve,..and as a result, swore out the concealed weapons charge. 1904 N.Y. Even. Post 10 Mar. 1 This position..was not such as the body would have taken had Newman been struck with a blackjack or other weapon. 1905 Ibid. 2 Sept., ‘I got a partner there [sc. in the penitentiary],’ Red said,..‘blackjacked a man.’ 1934 J. M. CAIN Postman always rings Twice iv. 31 She was to..clip him from behind with a blackjack I had made for her out of a sugar bag with ball bearings wadded down in the end. 1946 ‘P. QUENTIN’ Puzzle for Fiends (1947) xv. 106 Perhaps you gave a ride to a hitchhiker who blackjacked you.
