Just as a matter of fact, Haig so far as I've discovered, was not called "the butcher of the Somme" until the days of "Oh! What a Lovely War":

"It was the prototype Haig, the butcher of the Somme and Passchendaele, the ineffable forerunner of the inerrable Colonel Blimp...."

That's from Canadian Ralph Allen's World War 2 novel, "The High White Forest" (1964).

Before that, nothing.