There is no recorded evidence or historical documentation that Sithars used a specific name for vallarai keerai. The Tamil name for this leafy green vegetable likely predates the emergence of the "Sithar" tradition in Tamil culture.
It's important to remember that:
* Sithars are mythical figures: Their existence and practices are rooted in folklore and oral tradition, making it difficult to confirm the specific terminology they might have used.
* Language evolution: Tamil language has evolved over time, and terms used in ancient times might have changed or become obsolete.
Therefore, it's unlikely to find definitive evidence of a specific name that Sithars might have used for vallarai keerai.