Green’s Dictionary of Slang

(US) a sit-down meal, thus a square meal; spec. when a tramp is invited into a house and offered a meal indoors.

1893		Sun (NY) 21 May 28/1: ‘Well, dere’s some new people moved in and [...] dey give ye a set-down’ (a meal at a table).
1907		J. London Road 28: At the very next house I was given a ‘set-down.’ Now a ‘set-down’ is the height of bliss. One is taken inside, very often is given a chance to wash, and is then ‘set-down’ at a table.
1910		S.F. Call 17 July 11/2: For food he must have his trhee squares or ‘setdowns’ a day, and they must consist of meat, spuds, and ‘punk and plaster’ (bread and butter).
1921		P. & T. Casey Gay-cat 12: That kid don’t want no handouts. He gets setdowns [...] Setdowns in the kitchen.
1930		‘Dean Stiff’ Milk and Honey Route 85: I prefer to believe that the hobo [...] knows by instinct how to differentiate the houses where they give set-downs from the houses where they give only handouts.
1949		Monteleone Criminal Sl. (rev. edn).
1950		Goldin et al. DAUL 188/2: Set-down. (Hobo) A hot meal to which a hobo is invited.
1964		(con. 1920s–40s) in J.L. Kornbluh Rebel Voices.