1.) If the unit of space is in inches and the unit of force is in pounds the result is inch-pounds.

If the elastic limit is taken as the apex of the triangle the area of the triangle will represent the ~elastic resilience~ of the specimen.

This amount of work can be applied repeatedly and is perhaps the best measure of the toughness of the wood as a working quality, though it is not synonymous with toughness.
Permanent set is due to the ~plasticity~ of the material.

A perfectly plastic substance would have no elasticity and the smallest forces would cause a set.

Lead and moist clay are nearly plastic and wood possesses this property to a greater or less extent.