Different communities of Afghan Hindus and Sikhs have different histories. Following are some theories:
Hindus have always lived in Afghanistan. That’s one reason why they call themselves Kandharis and Kabulis.
Some of the old temples in the area also point to this theory. The word Kandh in Seraiki means wall. Kandahar used to have many walls. The Hilmand river flowing in that area was labeled “Rud-e-hind-wa-sind” by Arabic manuscripts. Before the influx of Pashtoons the inhabitants of Kandahar spoke Seraiki. The Pashtoons labeled their language “Jataki”. The language spoken by Afghan Hindus in Kandahar known as Kandhari is probably “Jataki”. (Information about the word Kandh, the Hilmand river and Jataki is from a Seraiki Linguist by the name of Ijaz Bloach.)
There’s Chahbra family in Bombay who traces his ancestory back to someone from Kabul from ten generations back.
The Afghan Hindus living in Kabul (Kabulis) are descendents of Hindu Shahis.
The Asamai mountain is actually named after the Hindu Goddes Asha Mai.
Ahmad Shah Baba in the 18th century brought few Hindu families from Multan and Sind area for commerce and the community grew and never left Afghanistan.
Some Sikhs and Hindus came to Afghanistan from Pakistan after the partition of 1947.
There are many families from India, mostly Sikh, who have the last name of Kandhari. I believe they are from Kandhar and were moved to Pakistan and India a century or more ago. Another theory is that they are descendent of Pir Vali Kandhari who was blessed by Guru Nanak.
By Satish Chander Ailawadi:
The roots of minority Hindu Afghan community can be traced back either to the rugged, barren, hilly region of Kandahar in Afghanistan or to Dera Ismail Khan in Pakistan’s North West Frontier Province. NWFP and Afghanistan were ruled by the Hindu king Kanishka and his Kushan dynasty till approximately the 7th century
A.D. , after which the Moghuls and Pathans took over. Down the centuries, the landlocked country was known
by three names- Aryana (where Aryans live) in ancient times, Khurasan (kingdom of King Kanishka) in the medieval period and now Afghanistan.
Alternatively called Pathans, Derewallas and Kandaharis, the entire Afghan Hindu community fled to India during the bloody days of partition. The language spoken by Kandaharis and Derewallas, the two dominant castes within Afghan Hindus, is a quaint mix of Pashtu (the language of Afghanistan), Punjabi and Persian, a relic of past.
The Afghan community comes from the rugged border regions of Baluchistan and the North West Frontier Province, the alkaline wasteland of Sindh, and the once Hindu-dominated Kush and Karakoram mountains embracing Kashmir.