This is all very interesting...John Laffin suggests that the term was first used in 1743 in a letter sent from Jamaica, but as to the reliability of this citation, I'm not sure. Its all fascinating because of the Irish attitude towards the war. It would appear that the general consensus was that the war was a terrible idea; 'The Flag of Ireland' published precisely the numbers of Irish soldiers in the various regiments sent to the Cape in 1879 - a critique, one might suspect, of Irish complicity - and much of the nationalist press came down heavily on the side of the Zulus (for instance the 'Chant for the Zulus' poem reproduced during the period of Zulu success in the early spring of 1879). I wonder therefore whether the Irish soldiers who fought were derided back at home for doing so? And if so, would the term 'Tommy Atkins' mean something completely different in Ireland than in England?