Green’s Dictionary of Slang

(S.Afr.) a diamond-buyer (often Jewish) who traded directly with miners on their claims; this practice was outlawed by the Diamond Trade Act (1882) hist.

1886		G.A. Farini Through Kalahari Desert 21: The wily Jew was a ‘partner’ in a ‘company’ of ten ‘Koppje wallopers’.
1887		J.W. Matthew Incwadi Yami 227: The kopje walloper was generally a gentleman of the Hebrew persuasion hailing from Petticoat Lane or the Monories.
1897		H. Raymond B.I. Barnato 14: The slang camp term [...] for this [i.e. diamond-buyer] was ‘kopje wallopper’, derived from the circumstance that in the earliest days the diamonds were obtained from a number of kopjes or small hills in the neighbourhood of the camp, and the dealers travelled on foot from one to the other purchasing the finds as they were turned out at the sorting tables .
1902		G.F. Williams Diamond Mines of S. Afr. 270: With this working capital he went into partnership with Louis Cohen, another new-comer, who had started as a kopje walloper.
1913		C. Pettman Africanderisms 278: Kopje walloper One who visited the diamond diggers at their claims in the early Kimberley days to purchase their diamonds.
1921		B. Williams Cecil Rhodes 43: Making his way up to Kimberley, he [...] turned his talents to the business known as that of a kopje-walloper.
1935		in Jewish Spectator (N.Y.) 35: ‘Another kopje walloper!’ the white digger exclaimed [...] Kopje walloper was a term of ridicule for the small diamond buyers.
1945		T.A. Rickard Romance of Mining 352: [He] become a ‘kopje-walloper’, or licensed dealer in diamonds.
1956		E. Hahn Diamond 87: He became what was known as a ‘kopje-walloper,’ a man who traveled from one digger’s house to another, buying stones.
1967		(con. 1870s) E.M. Slatter My Leaves are Green 38: Paul blinked ‘kopje-wallopers?’ ‘Diamond buyers.’.