mettlen

n. [ E. metal, used in a tropical sense in allusion to the temper of the metal of a sword blade. See Metal. ] Substance or quality of temperament; spirit, esp. as regards honor, courage, fortitude, ardor, etc.; disposition; -- usually in a good sense; as, to test a person's mettle. [ 1913 Webster ]

A certain critical hour which shall . . . try what mettle his heart is made of. South. [ 1913 Webster ]

Gentlemen of brave mettle. Shak. [ 1913 Webster ]

The winged courser, like a generous horse,
Shows most true mettle when you check his course. Pope. [ 1913 Webster ]

To put one one's mettle, to cause or incite one to use one's best efforts. [ 1913 Webster ]