The history of Onitsha began with the migration of its people from the Benin Empire towards the end of early part of the Sixteenth Century AD. The migration was as a result of a wave of unrest, war and displacement unleashed by the Islamic movement from North Africa.
It was during their passage through the outskirts of Ile-Ife that they acquired the name Onitsha - a corruption of the Yoruba word Orisha and Udo, the famous shrine worshiped by the people. As time went on, the combination of the two words, Onitsha for Orisha and Ado for Udo culminated in the present name , Onitsha Ado.
The people of Onitsha left the out skirts of Ile-Ife and resettled in the Benin Kingdom and soon established themselves as one of the clans in the Benin Kingdom exercising all the rights and privileges attached thereon.
As a result of a long process of acculturation in Benin, the Onitsha people jealously guarded their acquired rights particularly with regard to their revered Shrine Udo.
It was suggested that the reason why the Onitsha people quarreled with Oba Esigie, (1404-1550), of Benin was because of the slight, the Oba gave their shrine-Udo. It was customary for newly installed Oba to pay homage to all important Shrines in the Benin Kingdom by slaughtering a cow in the shrines enclave. Oba Esigie failed to do this at the Onitsha people's Udo-Shrine, hence the quarrel.
It took the Onitsha people several years before they got to Obior and Ilah and finally crossed the River Niger and established Onitsha Ado. They stopped at several places in the then Mid-West now called Delta State, places like Agbor, Issele-Uku, etc. This explains the affinity with the inhabitants of Delta State like Ilah, Issele-Uku, Obbaamkpa, Onitsha-Olona, Onitsha Ugbo, Agbo, Obior, Onitsha Ukwu and so on.
Another version hold that the people of Onitsha were part of the Edo tribe. It is for this reason that Onitsha people fondly call their town "Onitsha Ado N'Idu" meaning Onitsha of Edo Origin. It is also believed that the emigrants were nicknamed "Onitsha" only after their exodus from Benin by people whose territories they marched through, ravaging all that stood in their way. The name Onitsha has also been translated to mean dispenser. It reflects the manner the emigrants dealt with obstacles placed on their route by adjourning towns and villages.
All children roughly between the ages of ten and twenty years were known as Umu-Ilo. They are divided into three age-groups, the senior being in partial executive control of the rest, with power to levy small fines on any member who failed to turn out for any of the duties which devolved upon them. These duties are confined to the up keep and cleanliness, as understood by the Ilo, of paths, compound and open spaces.
Age Grade Proper:
After leaving the Umo-Ilo stage, young men would join together to form social clubs corresponding to the successive age-grades. Each grade or club adopted a name. The Ndiche would periodically select one of these grades to act as police in enforcing their decisions. The grade so selected would perform these duties for as long as it was considered capable of doing, after which it would hand over it's duties to another selected grade.
 Age Grades:
The age-grades still keep their separate identifies as social clubs, but Government with it's Police and Court Messengers has done away with the necessity for one of the age-grade to acts as they used to. A new body based on the age-grade system has, however, arisen to meet modern requirements. This body, know as the Ogbo Isato, is made up of the eight age -grades which have been formed from those who left the Umu Ilo stage after 1900.
It thus, comprises roughly all the young men in Onitsha between the ages of twenty and thirty-five years - i.e,. the young intelligentsia. The Ogbo Isato was founded with the objective of bringing non-partisan pressure to bear on the Ndichie in the settlement of the Obi succession and even if unsuccessful in this object it has come to be an unofficial power in the Town.
 Family Council
The administrative head of each family was the senior titled man. If there were Ndiche in the family, then he would be considered the senior, if only Ozo titled men, then the oldest one amongst them by age. In matters of any importance, however all the elders whether they had taken title of not, would attend as well all the titled men. At such a meeting, anyone would be allowed to air his views but the titled men would consult to decide the matter.
 Kindred Council
In each of the six kindreds the Ndiche Ume was the administrative head; or failing an Ndiche Ume, the senior Ndiche Okwa. In the kindred Council as in the family, any one who could command a hearing might express his views but only the title men would withdraw to consult.
 Town Administration
In all matters concerning Onitsha as a whole, or in any family or kindred affair which required an authorities order greater than that which the Ndiche concerned could give, the Obi was the final authority, though he was always first approached by, and considered the opinions of the Ndiche before giving his decision. Confined to his house most of the time as he was, the Obi would in practice take the advice of his Ndiche on most questions.
If they were divided opinion, he himself might try to obtain more detailed information from other private sources or alternatively send the Ndiche away to consult more thoroughly, and try to arrive at some single decision. But no measure adopted would be considered to be law until it had the Obi's consent and approval.