Green’s Dictionary of Slang

(US) third-rate liquor, also attrib.

1845		Subterranean 9 Aug. 2/4: The very worst species of three-cornered, grappling-iron swordfish. [Ibid.] 6 Sept. 3/2: This sword-fish den. [...] The deleterious character of the grappling-iron liquor which is dealt out to its besotted and depraved visitors.
1851		Life in Boston & N.Y. (Boston, MA) 28 June n.p.: Oh, ye gods — such ‘sword-fish!’ such ‘rot-gut’ never let it enter our bowels again!
1856		Life in Boston & N.Y. (Boston, MA) 25 Oct. n.p.: The mysteries of shaking down, shop-lifting, and gizzling swordfish gin.