Nirun Kot (present Hyderabad-Sindh), Debal, Sama & Lakha forts and the surrounding areas were populated by a Hindu community known as the Lohanas. This region was called Lohana Desh or Lohana Puraganas. Thattha and the surrounding region were also included in the Lohana Desh. Brahamanabad was their chief city

Members of the Lohana community were engaged in all types of trades, industries, animal husbandry and agriculture. They hearkened to the teachings of Gautama and were converted to Buddhism. In course of time, Buddhism lost its hold over the community and they became believers of the Shiva aspect of the Hindu Trinity, and a number of Devis and Devtas.

Eventually, as a result of the spread of the Islamic empires and long term occupation by the Muslim invaders, there was a heavy influence on the language, culture and lifestyle of the people in that region. In 1422 AD, Abu Zakaria Yahya Yusufuddin, a direct descendant of Shaikh Abdul Qadir Jilani of Baghdad came to Sindh to spread Islam. After labouring there for 10 years, he succeeded in winning over to islam 700 families of the Lohana caste. These 700 families, who had embraced Islam, formed in to a community and called themselves Momins, which means: true believers of Allah and faithful followers of Islam.

Over time, the word Momin was distorted, in the course of time, and the word Memon took its place.

Due to this conversion, a conflict arose between the neo-Muslim and the Hindu Lohanas with whom they had very close social relations. On Sayyid Yusufuddin’s advice, these 700 families migrated to Variya, which was situated near Thattha. A few years later, about 600 Memons migrated to Halar in Kathiawar and settled there permanently. They came to be called Halari or Halai Memons. A 100 years later, the 100 families remaining at Variya went to Bhuj, the Capital of Kutch to settle down permanently. They came to be known as Kutchi Memons. A few of these Kutchi Memons have migrated to Okha and have come to be known as Okhai Memons. Surat, in Gujarat was a n important trading centre from 1580 to 1680 and Memons made their bounty there. (Later, some of these Memons reached Bombay). While, Memon farmers who had opted to stay on in Southern Sindh were called Sindhi Memons.

These Memons in Kutch, Halar, Okha and Sindh stayed in their respective regions for a considerable period and developed characteristics and peculiarities region-wise and were markedly differentiated from each other. They later developed a sense of difference and pride, from one another, which regrettably exists even today.

Due to political upheavals, changing social patterns, call of professions, occupation or other prospects; Memons spread across the length and breadth of the Indian subcontinent and the world. Wherever they went, Memons formed themselves into Jamats. These Jamats are elected bodies and look after the welfare of the community.

References:
Excerpted from: “Memons: Their Origins and Brief History” by F.A. Chotani & A.M. Allana as published in the Memons International Directory, 1st edition 1971.
A History of Memons by Anwar Motan.
Races and Castes of Bombay Presidency by Anthovan.
The Preaching of Islam by T. W. Arnold
Islamic Perspective: A Biannual Journal. A special issue on Bohras, Khojas and Memons. Ed. by Asghar Ali Engineer, Bombay, Institute of Islamic Studies. vol.1, Jan 1988, pp. 192-211.