From the second edition (1989):
(blɪmp) [Of uncertain origin. Said to have been coined by the aviator Horace Shortt (see quot. 1918) or by Lieut. A. D. Cunningham (1951 Aeroplane 5 Oct.), and to have been based on the adj. limp.]

1. A small non-rigid airship orig. consisting of a gas-bag with the fuselage of an aeroplane slung underneath; in the war of 1939–45 the name was sometimes applied to a barrage balloon.

1916 Rosher In R.N.A.S. 11 Feb. 146 Visited the Blimps‥this afternoon at Capel. 1918 Illustr. Lond. News 27 July 96 Nobody in the R.N.A.S. ever called them anything but ‘Blimps’, an onomatopœic name invented by that genius for apposite nomenclature, the late Horace Shortt. 1926 J. R. R. Tolkien in Year's Wk. Eng. Stud. 1924 52 It is perhaps more in accordance with their looks, history, and the way in which words are built out of the suggestions of others in the mind, if we guess that blimp was the progeny of blister + lump, and that the vowel i not u was chosen because of its diminutive significance—typical of war-humour. 1928 Gamble North Sea Air Station x. 149 The Submarine Scout non-rigid type. The name was abbreviated to S.S. airships, but they were generally known as ‘Blimps’. 1934 Discovery Jan. 14/2 Excellent photographs‥could probably be secured next summer from a small ‘blimp’ carrying a pilot and a photographer and directed by wireless telephony. 1939 War Illustr. 29 Dec. 538/1 The term ‘blimp’ originated in the last war, when British lighter-than-air aircraft were divided into A-rigid, and B-limp (i.e. without rigid internal framework). The modern barrage balloon may therefore be classed as a blimp. 1940 Harrisson & Madge War begins at Home v. 125 The [barrage] balloons, so suitably called blimps, became a major symbol in the first three months of the war.

b. Cinematogr. A sound-proof covering for a ciné camera. colloq.

1936 C. B. De Mille in Words Oct. 6/1 A ‘blimp’ in studio jargon is‥a soundproof covering for the camera. 1959 John o' London's 3 Dec. 287/2 If I asked you to fetch me a ‘blimp’‥you might toss over‥a light cover to deaden the sound of a ‥cine camera, so that its whirring didn't get recorded on the sound track.

2. (Colonel) Blimp, a character invented by David Low (1891–1963), cartoonist and caricaturist, pictured as a rotund pompous ex-officer voicing a rooted hatred of new ideas. Hence blimp, a person of this type; also attrib. Also ˈblimpery, ˈblimpishness, ˈblimpism, behaviour or speech characteristic of a blimp; ˈblimpian, ˈblimpish adjs., typical of a blimp.

1934 Evening Standard 28 May 10 Prime Minister Blimp: ‘Gad, sir, the Air League is right. We must oppose all proposals for the abolition of military aviation.’ 1935 Ibid. 2 Sept. 15 Blimpian ‘statesmanship’—‘Gad, madam, you can't lock up the explosives! That's a warlike act!’ 1937 ‘G. Orwell’ Road to Wigan Pier x. 197 Easy to laugh at‥the Old School Tie and Colonel Blimp. 1937 F. P. Crozier Men I Killed 13 Blimp still reigns, unfortunately, in places of greater responsibility where he can make a fool of himself more easily. Ibid. vii. 137 Our new system of rearmament is at least serving the purpose of encouraging our Colonel Blimps to hide their heads‥in the sand. 1937 New Statesman 18 Dec. 1055/1 All to the good if people would be careful to send the full context and not send other people's ironical remarks or conscious jokes as if they were Blimpisms. 1938 Ibid. 5 Nov. 715/2 The modern clothes Hamlet at the Old Vic has excited a lot of Blimpish indignation. 1941 ‘G. Orwell’ Lion and Unicorn 44 Thirty years ago the Blimp class was already losing its vitality. 1941 N. Marsh Surfeit of Lampreys viii. 115 [He's] very nice.‥ Sort of old-world without any Blimpishness. 1942 Times 26 Feb. 8/3 The essence of blimpery is a refusal to entertain new ideas, and a determination to keep the bottom dog permanently in his place. 1943 C. Beaton Near East ii. 29 Blimpism, plus the Cairene climate, are two of Hitler's strongest weapons. 1944 H. G. Wells '42 to '44 147 The more Blimp-like officers began to exclude this ‘dangerous’ topic. 1958 Times 15 Oct. 8/7 His innate Blimpishness suddenly arrests itself and he sings a jolly nostalgic song about the cricket fields of Harrow. 1968 Daily Tel. 13 Dec. 16/4 His usual comic character of pub pundit or cockney blimp.