Today we write Sindhi in Arabic script, but is it true that the original script of Sindhi is Devanagari?
By Arvind Iyengar,
The short answer is: There is no clear answer to this question.
The answer to your question also depends on when you think the Sindhī language came into being, since languages change at a rapid rate.
The language of Shāh ʿAbdul Latīf Bhiṭṭāī (1689 – 1752 AD), the ‘national poet’ of Sindh, might be quite difficult to understand for a speaker of modern Sindhī. Therefore, can Shāh Latīf’s language be considered Sindhī?
That said, those driven by linguistic pride often claim (usually without proof) that the yet unknown language of the Indus Valley Civilisation was actually Sindhī, and therefore, the script used on the Indus Valley seals must be the original Sindhī script (even though no one knows what the symbols mean).
On similar lines, there might be those who claim that (depending on their ideology) either Arabic or Devanāgarī is the original script of Sindhī, again usually without proof.
A Sindhī translation of the Qurʾān and of the Mahābhārata are believed to have existed as far back as the 11th century (assuming of course that one can safely call this language Sindhī). Whether these were written in a Brāhmī-based script or an Arabic-based script is not clearly known (Brāhmī is the ancestor of the modern Devanāgarī script).
By the early 1800s, it has been attested by several authors, both Indian and European, that there were several different scripts in use for Sindhī, including Haṭavāṇikā (or Kẖudābādī), Gurmukhī and of course Devanāgarī and Arabic.