Green’s Dictionary of Slang

(US) a quilt or thick blanket, both used for outdoor sleeping.

1907		S.E. White Arizona Nights 18: Except for the very edges, which did not much matter, our blankets and ‘so-guns,’ protected by the canvas ‘tarp,’ were reasonably dry.
1913		H. Kephart Our Southern Highlanders (1922) 75: ‘Bill, hand me some Old Ned from that suggin o’ mine.’ [...] I learned that ‘Old Ned’ is merely slang for fat pork.
1915		M.G. Hayden ‘A Word List From Montana’ in DN IV:iii 245: soogan, n. Sheep herder’s blanket. ‘When they move, they just roll up the soogan and are off.’.
1927		Chronicle-Telegram (Elyria, OH) 30 Sept. 3/1: The corral rope was on his saddle, next to the sougan.
1929		V.W. Saul ‘Vocab. of Bums’ in AS IV:5 345: Sugan—A bed quilt.
1930		D.I. Young ‘The Pioneer Dance’ in Botkin Folk-Say 262: Parents of several brought heavy wraps and soogins to provide against the sleepy time of their four- and six-year olds.
1931		Irwin Amer. Tramp and Und. Sl. 176: soogan.–A blanket or comforter carried by a tramp or migratory worker. From the Montana and Wyoming range country, where the cow-punchers and sheep-herders originated the name.
1938		B. Conlon ‘Rope Meat’ in Wild West Weekly 22 Oct. 🌐 He had taken [...] all his ammunition, saddle, bridle, reata, braided stake rope, his soogans and tarp.
1938		(con. c.1910) S.H. Holbrook Holy Old Mackinaw 192: Blankets are sougans.
1939		P.A. Rollins Gone Haywire 62: The blankets might be of ordinary commercial manufacture, or they might be soogans, otherwise known as suggans—homemade coverlets created from numerous fragments of discarded garments [DA].
1947		W.D. Overholser Buckaroo’s Code (1948) 33: Me and Bill are getting our soogans, and riding down to Slow Spring.
1964		(con. 1920s–40s) in J.L. Kornbluh Rebel Voices.
1995		Santa Fe New Mexican (NM) 17 Mar. 15/5: New Mexico’s traditional ‘sugans’ (also known as cowboy quilts).