Reference for Nedarim 45:5
אמר ליה רב אחא מדיפתי לרבינא האי נולד הוא דלא מסיק אדעתיה דמחי ליה קצרא ותנינא אין פותחין לו בנולד אמר ליה האי לאו נולד הוא דשכיחי אפיקורי דמצערי רבנן
— He replied: This is not unexpected, because scoffers<span class="x" onmousemove="('comment',' Apikora (pakar) etymologically should mean a loose, unbridled person. Its phonetic similarity phonetic similarity to Epicurus, the philosopher, stamped it with the meaning of sceptic, heretic, and that is its probable meaning in Sanh. XI, 2, where an apikoros is excluded from the world to come. The definition given in the Gemara, 99b, viz., one who is scornful of the Rabbis, which is the same as it bears here, was in all probability an extension of its meaning, due to feuds between the Rabbis and some sections of the people. ');"><sup>4</sup></span>