Green’s Dictionary of Slang

1. one who deliberately avoids military service, esp. by securing a post in a government office or the civil service.

1918		E.T. Cook Literary Recreations 163: A generic name, Cuthbert, has been given to supposed shirkers.
1918		Godwin’s Wkly (Salt Lake City, UT) 26 Jan. n.p.: The slicker is a slacker who is smart enough to get a bomb-proof position that will entitle him [to] be, inferentially, in drawing-room and clubs, a hero. Over in England [...] they call them ‘Cuthberts’.
1919		C. Garstin Mud Larks 82: Next morning the Babe dug up an old suit of 1914 ‘civies’ and put them on. A woman in the Tube called him ‘Cuthbert’.
1921		N&Q 12 Ser. IX 383: Cuthbert. A stay-at-home, especially in Government offices.
1924		(con. WWI) A.G. Pretty Gloss. of Sl. [...] in the A.I.F. 1921–1924 (rev. t/s) n.p.: cuthbert. A man with a cushy job in a Government Office, esp. one who avoided Military Service on the score of occupation. Personal name supposedly suggestive of effiminacy.
1984		Partridge DSUE (8th edn) 264/1: from 1917 (ob.).

2. a conscientious objector.

1948		Partridge et al. Dict. Forces Sl.
1994		(ref. to WWI) Bryant & Heneage Dict. British Cartoonists and Caricaturists 72: His most famous creations were John Citizen, Cuthbert the World War I conscientious objector, Dilly and Dally [etc.].