The reason behind Sindhi Surnames

Why do many Sindhis have their surname end with "ani". Is there any logic behind it?

Yes, There is a Logic Behind this
Here's a piece of information picked up from another sites, which all Sindhis and communities should know!

Unlike other Hindus of India, who have a 'gotra', Sindhis often have a 'nukh', which means roots. This is much of the reason why Hindu Sindhi surnames end in 'ani'- which means 'anshi', derived from the Sanskrit word 'ansh', which means 'descendence'. So if someone returned or came from Georgia, his nukh would be 'jeorus', and his surname could be coined after the family head's name (subject to change every seven generations), eg: your family head 7 generations back had the name: 'Tolaram', then your surname would be TOL-ANI. Same goes for all the ani's in the world. May the person be from Iran, Iraq, Saudi Arabia, Italy, Anatolia, Armenia or wherever, as this 'ani' is only unique to Sindhi civilization.

Another variation does exist to this norm. Many surnames of northern Sindh eg: (Shikarpur) and Multan (ancient name: Sawarawkistan) end in 'ja', eg: Ahuja, Raheja, Hinduja etc. 'Ja' in Sindhi means 'of', so if a person belonged to the village of 'Junay', then their surname would be 'Juneja'.
Now the Question arises, why is there a need to add 'ani' or 'ja' to Sindhi surnames? It's because, post Mahmud Ghaznavi invasion, many Sindhis had escaped. They were called 'Banjaras' in India, Sinti in distant European lands, and 'Sintowee' in Mongolia and China. 'Gypsy' is a term used for them frequently. However, many Sintis awaited the end of Ghaznavid rule, so that they could return back. Many did return back, but many were pushed westwards, and thus have never returned. Those who managed to return are called 'AARYAN', which is a term different to the sanskratic version 'ARYA'.

AARYAN in Sindhi means those who have come back. These tribes added 'ani'(southern sindh) and 'ja' (northern sindh) to their names. Already an Indo-Iranian race, the Sindhi Hindus, once becoming Sintis in distant lands acquiring a range of cultural habits of different cultures, and furthermore with many inter-cultural marriages, the fabric in the race of Sindhis varied tremendously. Different dialects in Sindh were born, and different dressing sense as well. The Aamil Sindhi for example were a cross-breed of Indo-Iranian Sindhis and Alexandrian Greeks, and thus emphasized more on education.

The Bhaibund and Shikarpuri Sindhis, who returned back (Sintis) from Armenia, Turkey and Egypt, brought with them business skills and tactics. There are many more variations in the community, and it is quite difficult to identify who belongs where. Thus, 'nukhs' are the only way to identify one's roots. Furthermore, due to constant upheaval of Sindhis, and further migration and amalgamation with different migrant tribes, a lot has changed, and Sindhi music and dance post Islamization has not remained the same. In such a scenario the Sinti music of the Gypsies can be called the pure sindhi dance and music. Islamization of Sindh further brought about Sufism, which further enhanced the culture of Sindh
As the size of families grew within the Gotra, need arose to identify each family by name. Each family was alotted a Nukh (Name), which helped to identify one another. From Nukh one knew which Gotra one belonged to.

In Sanskrit word for Nukh is Lakh, meaning Laksh which in Sindhi is pronounced Lakh, meaning to know from where one hails.

Gautam Rishi’s Gotra were allotted Nukh called AVER, UDECH & AAEN, who were Brahmins.

Khatris and Vaishas had their own Goters. They were also allotted Nukhs.

Advani’s of Hyderabad Sind carry Nukh named "Maghoo Khatri". Ahuja & Makhija are names of their Nukh.