Fatwood
Fatwood, also known as "fat lighter", "lighter wood", "rich lighter", "pine knot", "lighter knot", "heart pine", "fat stick" or "lighter'd" [sic], is derived from the heartwood of pine trees. The stump (and tap root) that is left in the ground after a tree has fallen or has been cut is the primary source of fatwood, as the resin-impregnated heartwood becomes hard and rot-resistant after the tree has died.