Green’s Dictionary of Slang

of a soldier, to be demobilized.

c.1918		H. Champion [perf.] ‘Any Old Rags’ 🎵 I got demobbed, with my hair all bobbed.
1920		Glasgow Herald 2 June 11: Some young soldiers [...] who had been recently demobbed .
1934		Weseen Dict. Amer. Sl.
1945		Daily Mirror 11 Aug. 3: [headline] It’s ‘total’ demob. now—Many home by year’s end .
1959		F. Norman Fings II i: I’m goin’ ter marry my boyfriend. ’E gets demobbed on Thursday.
1973		B.S. Johnson All Bull 25: When I was demobbed they bought me ten quid’s worth of paint as a farewell present.
1997		A. Frewin London Blues 44: I started in the Chatham dockyards in 1946 as soon as I was demobbed.