The bank descends from the Bank of Calcutta, founded in 1806, via the Imperial Bank of India, making it the oldest commercial bank in the Indian subcontinent. The Bank of Madras merged into the other two "presidency banks" in British India, the Bank of Calcutta and the Bank of Bombay, to form the Imperial Bank of India, which in turn became the State Bank of India in 1955. The Government of India took control of the Imperial Bank of India in 1955, with Reserve Bank of India (India's central bank) taking a 60 % stake, renaming it the State Bank of India. In 2008, the government took over the stake held by the Reserve Bank of India.

Based on this passage, what is the old name of state bank of india? Let's think fast. Stream of consciousness:
The relevant sentence in the passage is: The bank descends from the Bank of Calcutta, founded in 1806, via the Imperial Bank of India, making it the oldest commercial bank in the Indian subcontinent. So the final answer is the Bank of Calcutta.