Dhirubhai Ambani, founder of Reliance Industries, is credited with coining the term 'mega issue' in the Indian business context, referring to large-scale public share offerings. His vision of democratizing wealth through public participation in business led to this concept. The other options - Narayana Murthy, J.R.D. Tata, and Mukesh Ambani - are prominent industrialists but not associated with coining this term.