Green’s Dictionary of Slang

barrel-boarder n.

also barrel dosser, barrel-house stiff, barrel stiff
[SE barrel + SE boarder/dosser n. (1)/barrelhouse n./stiff n.1 (5a)]

(US) an ageing, impoverished, poss. alcoholic tramp who frequents low drinking saloons.

[UK]Farmer & Henley Sl. and Its Analogues I 135/1: Barrel-boarder, subs. (American) – A loafer in low drinking-saloons.
[UK]W.H. Davies Beggars 47: The sole occupation of a barrel-house stiff is to stand outside public-houses waiting for invitations to drink [...] There is not often more than one or two barrel stiffs to one house.
[UK]W.H. Davies Adventures of Johnny Walker 56: The barrel-house-stiff is the most despised of all stiffs, for the simple reason that he is a physical wreck [...] The barrel-house-stiff is the shortest liver of all stiffs.
[US] ‘Jargon of the Und.’ in DN V 438: Barrel-dosser, The lowest order of bums who sleep in and live upon the offal of barrel-houses. Also barrel-stiff.
[US]Irwin Amer. Tramp and Und. Sl. 22: Barrel Dosser. [Ibid.] 23: Barrel Stiff.—An old, worn-out bum, living in barrel houses, eating whatever may be salvaged from garbage cans or cheap lunch rooms, and absolutely without hope or ambition.
[US]Monteleone Criminal Sl. (rev. edn) 17: barrel dosser A tramp who frequents barrel houses [...] barrel stiff A low-class tramp who frequents barrel houses.
[US]Ragen & Finston World’s Toughest Prison 790: barrel-stiff An old worn out bum living in barrelhouses.