Green’s Dictionary of Slang

openly, honestly, in a straightforward manner; also as adj., open, honest, straightforward.

[1871		S.F. Chron. 26 Nov. 1/4: [They] entered into a dispute, which was ended by Shaffer striking King on the nose and the reply of King straight from the shoulder].
1895		Wilkes-Barre Times Leader (PA) 23 July 4/5: We always talk straight from the shoulder. Mean what we say and back it up.
1890		Times-Democrat (New Orleans, LA) 9 Feb. 4/2: The Mayor is himself too much of an expert in hitting straight from the shoulder, in a metaphorical sense .
1900		Falkirk Herald 12 Dec. 6/2: To-day I want to talk to you for five minutes straight from the shoulder.
1910		Pittsburgh Press (PA) 11 Sept. 46/1: If to ‘talk straight from the shoulder’ signifies directness of aim and weight of blow, I should strive after both.
1920		in A. Cornebise Amaroc News (1981) 4 July 160: He speaks from experience [...] and he delivers his ‘jolts’ straight from the shoulder.
1928		Norwood News 27 July 2/3: Mitcham Council had it straight from the shoulder from one of the residents.
1932		E.S. Gardner ‘Bird in the Hand’ in Goulart (1967) 266: I’m a girl that shoots right straight from the shoulder, that’s me.
1945		in T. Shibutani Derelicts of Company K (1978) 208: He’s really a regular guy – straight from the shoulder. He never fucks you from behind. [Ibid.] 318: He’s really square from the shoulder. He never fucks you up.
1952		(con. 1933) G. Fowler Schnozzola 160: I always speak my mind. I run my business that way, right from the shoulder.
1969		A. Buzo Rooted II i: I’ll have a man to man chat with him. Off the cuff. Straight from the shoulder, no punches pulled.
1978		R. De Christoforo Grease 95: Danny has always been straight-from-the-shoulder with me.