Do we know how far back Apiqoros goes in Hebrew? To the time of the Maccabees?
Best I can tell, the word has been around since Epicurus. Yet, it looks like we first have the term attested in text just a generation after the invasion of the Maccabees. The word is used in "the early Tannaitic sources (first century before Hillel)" where it is used "to refer to one who espouses Epicurean philosophy."
There is a tradition of denying that the term comes from Epicurus, while nevertheless understanding that is really does come from him. Happily the handbook even mentions this open deception "It is also worth bearing in mind that the Talmudic etymology of the term may itself be a self-consciously homiletic effort rather than a serious philological one" (pg 567). Meaning the argument that it is unrelated is not even believed by those who make the argument.
Also, the argument that the word means "heretic" in a general sense may also be disingenuous -- at least originally it specifically means "Epicurean."
(Avot 2.14) "know what to respond to an Epikoros"
(Sanhedrin 10.1) "These are they who have no place in the world to come: He who says there is no resurrection of the dead, that there is no Torah from Heaven, an Epikoros"
The advice to, (if legally possible) publicly kill Epicureans (but if not legally possible) to kill them by deception is hardly a unique treatment for those who disagree -- although the bit about leaving us to die in wells by "temporarily borrowing" our ladder (if the opportunity should arise) is a unique little twist!