Septem, Octo, Novem, Decem. Seven, Eight, Nine, Ten in Latin. The last three letters forming the final syllable of all month names is -ber. Yes, Septem ber, Octo ber, Novem ber, Decem ber.
Yes, October is consistent with September, November and December.
So, there! All you Octemberists can stop it now.