Viable originated in 1828, from French viable "capable of life" (1530s), from vie "life" (from Latin vita "life," from PIE root *gwei- "to live") + -able. Originally of newborn infants; generalized sense is first recorded 1848. What is your smallest viable market? What is your product for? Who is your product for? What change are you seeking to make? Be specific with your smallest viable market. Start small and grow.
Viability, become capable of life, create a market