Green’s Dictionary of Slang

to render a victim unconscious with chloroform, usu. to rob them or carry them aboard a ship in need of crew; thus locusing n.

1831		Examiner (London) 764/2: May threw a glass of the gin into Bishop’s tea, when the latter said, ‘are you going to locus or Burke me?’ Mr. Horner explained that ‘locus’ was a cant word to describe the act of putting a man in a state of stupidity. [The report of the same case in John Bull 5 Dec. 386/3 has: ‘Are you going to hocus (or burk) me’.] .
1831		Satirist (London) 27 Nov. 237/2: Duchess—But what does locussing mean? Chev[alier].—Me will tell a you. Suppose you tell ame to bring you de great black boutell of de corjall dot be your grand favoureet, and me put mosh vat you call opium at de inside, and you take de big dreenk as at odor times. Den, you see, you get bodered, and so you be de locust .
1839		Port Phillip Gaz. (Vic.) 20 Apr. 2/3: [W]ith the death rattle in his throat, his last expression was that he had been ‘locasied,’ a slang term [...] signifying that poison or other unfair means had been made use of to get rid of him while in a state of partial intoxication.
1859		Hotten Dict. of Modern Sl. etc. 60: locuss to drug a person and then rob him. The LOCUSS generally consists of snuff and beer.
1868		‘Six Years in the Prisons of England’ in Temple Bar Mag. Nov. 539: Locusing is putting a chap to sleep with chloroform.
1941		Baker Popular Dict. Aus. Sl. 44: LOCUS AWAY: To shanghai a man while he is under the influence of liquor.