"not in accordance with established doctrines," 1630s, from Greek heterodoxos "of another or different opinion," from heteros "the other" (see hetero-) + doxa "opinion," from dokein "to appear, seem, think," from PIE *dok-eye-, suffixed (causative) form of root *dek- "to take, accept."
<a href="https://www.etymonline.com/word/heterodoxy">Etymology of heterodoxy by etymonline</a>
Harper, D. (n.d.). Etymology of heterodoxy. Online Etymology Dictionary. Retrieved $(datetime), from https://www.etymonline.com/word/heterodoxy