Green’s Dictionary of Slang

a thief who specializes in stealing goods from the back of vans and carts; thus van-dragging; but note cite 1938.

1926		N. Lucas London and its Criminals 270: The finest guard against ‘van-draggers’ is to employ boys to ride in the vans and never leave them as is the practice of many transport agents.
1930		Eve. Herald (Dublin) 9 Dec. 4/6: Other [underworld] terms include : — ‘Flatty’ (policeman), ‘peach’ (to give away), ‘Peter’ (safe), ‘monkey’ (padlock), ‘stick’ (jemmy), ‘van dragger’ (motor thief), ‘snow’ (cocaine), ‘madam’ (misleading conversation) ‘stir’ (prison).
1936		Sunshine Advocate (Vic.) 11 Sept. 6/3: Those who steal parcels from delivery carts are ‘van draggers’.
1938		Hartlepool Northern Dly Mail 15 Jan. 7/3: Car are ‘jam jars’ and those who steal them [...] ‘van-draggers’.
1977		D. Powis Signs of Crime 181: ‘Van dragging’ means stealing from motor vehicles.
1981		(con. c.1907) A. Harding in Samuel East End Und. n.p.: preface: Giving evidence before the Royal Commission on the Metropolitan Police in 1907 [...] he was described as the ‘king’ or ‘captain’ of the Brick Lane van-draggers. [Ibid.] 112: Most of them got their time for van-dragging.