Then, when a bipartisan immigration deal was proposed in the Senate, it was Trump’s turn to wield the A-word to bury it. In a tweet, he said the bill would create “a giant amnesty,” echoing a statement from the Department of Homeland Security that it was nothing more than a “mass amnesty bill for illegal aliens of all ages.” The bipartisan bill and a Trump-backed alternative went down to defeat in the Senate, both tarnished by the mere association with the word “amnesty.”

So how did “amnesty”—a word that politicians of both parties once used to invoke generosity and openness—become such a monstrous taboo? Its very invocation has scuttled attempts at immigration reform year after year. Despite its recent weaponization, the usage of the word “amnesty” has actually been rather benign over most of its history. But its more recent shift offers a window into the growing potency of immigration in American politics.

In today’s debate, amnesty has come to carry a sense of getting off scot-free, a kind of unearned forgiveness, but its origins lie in the more benign idea of forgetting. The word originated as “amnestia” in ancient Greek, with the same root as “amnesia.” Even in classical times, this word for not-remembering could also refer more specifically to the pardoning of a crime against the state. The historian Plutarch relates that after the assassination of Julius Caesar, the great Roman statesman Cicero “persuaded the senate to imitate the Athenians and decree an amnesty for the attack upon Caesar.” In English, “amnesty” was borrowed in the sixteenth century with a similar legal understanding, equated to an “act of oblivion” from the government to forgive someone of past offenses.