From the Indus River or the country of India
Indiah is a modern spelling variant of the name India, which is derived from the name of the Indus River. The river's name comes from the Sanskrit word 'Sindhu', meaning a large body of water. This specific spelling adds a decorative 'h' at the end, a common trend in contemporary English naming.
Less common today
Indiah isn't in the latest US Top 1000. It last peaked at #6,735 in 2000.
US births per 5-year period, 1990βpresent (SSA data).