Better known in English as an octet, which is closely related (more on that anon). In this form, it is often used specifically to refer to a group of eight creation gods worshiped* around Hermopolis during the Old Egyptian Kingdom (dynasties 3-6, running roughly 2686-2134 BCE in the standard dating). This ogdoad comprised four male-female pairs: Nu and Naunet represented the primordial water, Amon and Amaunet represented air and hidden powers, Kuk and Kauket represented darkness and obscurity, and Huh and Hauhet represented eternity. Yes, those are just masculine/feminine forms of the same name -- the members of each pair are otherwise indistinguishable to us.
The word arrived around 1620 via Latin from Greek ogdoás, a group of eight, derivative (using the feminine suffix -as denoting descent from or connection with) of ógdoos, eighth, from oktō, eight -- octet having being derived directly from oktō, without the intervening Greek declension.
* Why the heck is it worshiped and not worshipped? Was the English language drunk when it swiped that word?