Actually if you look at the history of anarchism you'll find it was the ancaps who tried to redefine the word, not the other way around. Murray Rothbard, one of the founders of anarchocapitalism literally says this almost verbatim.
‘One gratifying aspect of our rise to some prominence is that, for the first time in my memory, we, “our side,” had captured a crucial word from the enemy . . . “Libertarians” . . . had long been simply a polite word for left-wing anarchists, that is for anti-private property anarchists, either of the communist or syndicalist variety. But now we had taken it over. . .’ [The Betrayal of the American Right, p. 83]
‘One gratifying aspect of our rise to some prominence is that, for the first time in my memory, we, “our side,” had captured a crucial word from the enemy . . . “Libertarians” . . . had long been simply a polite word for left-wing anarchists, that is for anti-private property anarchists, either of the communist or syndicalist variety. But now we had taken it over. . .’ [The Betrayal of the American Right, p. 83]