The word heresy comes from the Ancient Greek word haeresis which literally translates as “something that was chosen.” A choice. The word haeresis carried no negative connotation for the Greeks. An haeresis was the result of someone using their reason to decide between competing options. Haeresis was the result of deliberation. Making an informed choice was considered a sign of wisdom.
The meaning of the word began to change with the nascent ascendancy of the Catholic Church in the first millennium. To the church and its leaders, people thoughtfully considering their options and making an independent choice - a heresy - was not just bad, it was dangerous. The very last thing that church authorities wanted was to be surrounded by people with the temerity to think for themselves.