Okpanam which accounts for the preponderance of migrations among the Igbos in Delta State (Anioma) is the cradle of Anioma civilization.
The root of Okpanam is Nri/Igala.

I’m from Anam. Okpanam and Anam are brothers. Even now we must consult with Okpanam on major endeavors. https://twitter.com/favy_c/status/1254326247989088256">https://twitter.com/favy_c/st...

Our other brother is Olosi (Edo State), Anaku and Nzam. Nzam still speaks Igala.
Prof Isichei and Afigbo have done a through work on our history (see excerpts from Afigbo below)

If I speak Anam, you’ll be hard put to understand it.
We’re all very proud to be Igbos

If you ever visit Okpanam pay a visit to the Ogbe shrine. It’s located at the marketplace in the town center