Green’s Dictionary of Slang

1. (US, also ruben) a country bumpkin, a farmer; also generically.

1804		‘Reuben’s Nutbrown Maid’ in Nightingale 284: But she, tho’ conscious of his worth, Had chose a youth more rare; A rustic Reuben was his name [DA].
1855		Herald of Freedom 8 Sept. 2/5: letter signed ‘Reuben Rustic’ [DA].
1890		W.T. Hall Turnover Club 49: And I overheard one of a knot of Ruebens standing on a corner say [etc.].
1901		St Louis Republican (MO) 26 May 41/6: When reuben comes to town / He’s sure to be done brown.
1907		Leavenworth Echo (WA) 12 Apr. 3/2: The fraternal brotherhood have a hay-makers hop advertisied [...] If all the Hey Reubens and Sally Anns turn out [etc.].
1907		Quad City Times (Davenport, IA) 17 Nov. 9/1: When the ruben legislator Blows in Dav. to get a Skate or Rubber at the living pictures when the red light is in bloom.
1912		‘Ta-Ra-Ra Boom Dee-Ay’ in Lingenfelter et al. Songs of the Amer. West (1968) 494: Part of that machine / Hit Reuben on the bean.
1916		J. Lait ‘Canada Kid’ in Beef, Iron and Wine (1917) 157: The Canada Kid, our nimble-fingered friend, had just returned from a voyage of reprisal among the Reubens, toiling here and there [...at] gatherings of the rural yeomanry.
1921		P. & T. Casey Gay-cat 147: They [...] breaks inter the keester o’ the bank safes, an’ gits away with all the stored-up jack of all them reubens round about.
1927		C.M. Russell Trails Plowed Under 65: Two or three of these Reubens would be easy for him.
1930		G. Milburn ‘The Dealer Gets It All’ in Hobo’s Hornbook 151: But the reubens they was horstile, and they banded forty strong.
1958		(con. 1940s) B. Behan Borstal Boy 273: He seemed even a bit more thick than Reuben on the Garden party.
1964		(con. 1920s–40s) in J.L. Kornbluh Rebel Voices.
1975		H. Ellison ‘Neon’ in Deathbird Stories (1978) 189: When the marks, kadodies and reubens fresh from Michegan’s Ionia State Fair descended on sinful Times Square.
1989		H. Rawson Dict. of Invective (1991) 192: As for country dwellers, in addition to hick, names and nicknames that have been used disaparagingly as generics include: [...] Reuben.

2. a fool, a gullible person, irrespective of geography.

1902

Ade Forty Modern Fables 268: About the Time that he was 40 and a confirmed Reuben, he got in with the Rise in Industrials, and the Wave of Prosperity carried him out of the Hall Bed-Room and landed him in a Suite that he called a Suit.