Why was the 1973 Budget called the Black Budget?

India's Union Budget for 1973-74 was called the 'Black Budget' as the nation had a deficit of ₹550 crore. The Budget was presented on February 28, 1973, by then Finance Minister in the Congress government, Yashwantrao Chavan. Interestingly, the 1997 Budget presented by P Chidambaram was called the 'Dream Budget' owing to the reforms which helped broaden India's tax base.