Made Of Sterner Stuff Meaning

(idiomatic) strong and determined (especially more so than someone else, to whom one is being compared).

Example: 2011 September 18, Ben Dirs, “Rugby World Cup 2011: England 41-10 Georgia”[1], BBC Sport:
  When Hape sauntered over for a try after only three minutes it looked as if England were destined for a comfortable victory, but Georgia are made of sterner stuff, as they showed when running Scotland close in Invercargill last week.
1933, Barnaby Ross, Drury Lane's Last Case, March 1946 republication as by Ellery Queen, Little, Brown, page 45:
  […] sign hung from the bronze knob, and it stated without equivocation that the Britannic Museum was "closed for repairs."
  But the Inspector was made of stern stuff. He closed his right hand and with the resulting fist pounded formidably on the bronze.
  […] out popped the gargoylish head of a bulb-nosed old man.
  "Hey!" snapped this apparition. "Can't you read English?"
  "One side, brother," said the Inspector cheerfully. "We're in a hurry."
  The doorman did not budge […]