Where does “haereticus” come from?

haereticus (Latin) comes from Ancient Greek αἱρετῐκός, from Ancient Greek αἱρέω, from Proto-Hellenic həřřéyō, from Proto-Indo-European sēr-, from Proto-Indo-European ser- — to flow; to guard; to bind, to tie together.

haereticus (Latin): heretical; heretic