Pith

n. [A-S. pidha, D. pit, pith, kernel; L. Ger. peddik.]

1. The soft, spongy substance in the center of many plants and trees. It consists of cellular tissue.
2. (Anat.) The spinal cord; the marrow. Ray.
3. Hence, that which contains the strength or life; the vital or essential part; concentrated force; vigor; strength; importance. “That's my pith of business.” Shak.

Enterprises of great pith and moment. Shak.