From the second edition (1989):
(ˈpɒplərɪz(ə)m) [f. Poplar, the name of a district, formerly a borough in the East End of London + -ism.]

The policy of giving out-relief on a generous or extravagant scale, practised by the Board of Guardians of Poplar about 1919 and later; any similar policy which lays a heavy burden on ratepayers. Hence ˈPoplarist, one who practises or advocates Poplarism; also attrib.; ˌPoplariˈzation, the adoption or implementation of Poplarism; ˈPoplarize v. trans., to make like Poplar; to subject to Poplarism.

1922 Glasgow Herald 3 Nov. 8 The hard-headed workers of Yorkshire‥have learned the lesson of Poplarism. 1923 Daily Mail 31 July 5/3 ‘Poplarism’ was a portent of the changing of the modern state. 1923 R. Macaulay Told by Idiot i. 44 So Poplarised‥did she become that she took to speaking of her parental home in Bloomsbury as being in the West End. 1923 Glasgow Herald 1 Oct. 8/6 A decision in the opposite sense would simply mean an indefinite continuance of the Highland variety of ‘Poplarisation’ in the Lewis. 1924 Ibid. 7 Apr. 12/4 Mr. Wheatley‥had been accused of desiring to ‘Poplarise’ the British people. 1925 Ibid. 6 Mar. 9 Even the cautious prophets‥foretell the announcement of a rebuff to the Poplarists tomorrow. 1928 Daily Tel. 6 Nov. 12/6 Those‥will demand increased subsidies, allowances, and ‘Poplarised’ social services, to be paid for out of the proceeds of very high taxation. 1931 Times 20 Feb. 7/6 The chief issue of the election is whether or not the policy of ‘Poplarism’ advocated by the Labour-Socialist Party is to be applied to London government. 1962 B. Keith-Lucas in Public Law Spring 67 The central government was finding that the weapons available to it were inadequate for the purpose of defeating Poplarism. The Poplar Order was being defied week by week. 1973 G. W. Jones in Ibid. Spring 28 Morrison had been opposed to the three elements of ‘Poplarism’, the payment of excessive wages and excessive relief and the refusal to honour legal obligations. 1976 H. Wilson Governance of Britain ii. 29 It was all done by agreement, Snowden recording that, as George Lansbury had to be found a job, despite his ‘Poplarist’ reputation, it was he who suggested Lansbury for the Office of Works.