Mettle /(?)/

Met·tle

Mettle

n.
  1. 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.
    A certain critical hour which shall . . . try what mettle his heart is made of.
    Gentlemen of brave mettle.
    The winged courser, like a generous horse, Shows most true mettle when you check his course.

Phrases & Compounds
To put one one's mettle
to cause or incite one to use one's best efforts.