'apikorsim' originates from Hebrew/Aramaic, specifically the word 'apikoros', ultimately derived from the Greek name 'Epikouros' (Epicurus).

'Epikouros' (Greek) was used in rabbinic Aramaic/Hebrew as 'apikoros' meaning a follower of Epicurus or someone who denies providence; it passed into Yiddish as 'apikores' and into English in forms such as 'apikoros', 'apikores' and the plural 'apikorsim'.

Initially it referred to followers of the philosopher Epicurus; over time in Jewish religious literature it came to mean 'heretic' or one who denies religious doctrine, which is its common modern sense.