Green’s Dictionary of Slang

dug-out n.1

[SE dugout, a roofed shelter used in trench warfare; note Fraser & Gibbons (1925) suggest: ‘It first came in apparently during the South African War of 1899–1902 for pensioned or retired officers who came back to service in consequence of the depleting of the active establishment through casualties in the field’, however, first citation in the OED is 1912]

an old-fashioned person, either in ideas or appearance, esp. a retired officer etc, recalled for temporary military service.

Show quotations
[UK]Blackwood’s Mag. June 805/2: From his turn-out, he was probably a prehistoric ‘dug-out’, a ‘was-bird’ of ‘weird’ early Victorian ideas .
[Scot]‘Ian Hay’ First Hundred Thousand (1918) 48: Even dug-outs like me are rare and valuable objects at present.
[UK]J. Buchan Greenmantle (1930) 182: Uniforms were everywhere, but their wearers generally looked like dug-outs or office fellows.
[UK]C.E. Callwell [bk title] Experiences of a Dug-out, 1914–1918.
[UK]A. Christie Three Act Tragedy (1964) 136: That dear old dug-out?