Moderator 80,
Thanks!
A quick Google search found the following by Gail Lichtman in the Jerusalem Post:
“According to Rabbi Shlomo Yosef Zevin, in his authoritative work Moadim Behalacha, the earliest reference in halachic literature prohibiting eating kitniyot during Pessah is found in the 13th-century book Sefer Mitzvot Katan (“A Little Book of Mitzvot”) by the Ashkenazi sage Rabbi Yitzhak Ben-Yosef of Corbeil. Rabbi Yitzhak refers to the prohibition, not as a new custom but as one “from the times of previous sages,” indicating that the custom was already well-established in his time. “
This was long before Columbus so I don’t see how maize could have been part of that original prohibition unless the Ashkenazic sages had nevuah to prohibit something no Jew had ever seen!