Vital endurance

Discussions yesterday led to the questions:

"What does vital mean?"
"What does endurance mean?"
"What is the opposite of endurance?" (This one stumped us.)
"Would delicacy be the opposite of endurance?" (Um, no.)
We settled on fragility as an antonym for endurance. At which point it became part of the title for a blueprint (plan drawing on white paper, although we have previously discussed why it might be blue) of a level design for Angry Birds Knock on Wood (which is made of plastic, not wood).
Today, while playing one of our recent favorite DS games, "Is stats short for statistics?"
Most anything can prompt our curiosity.
(Now where did the phrase knock on wood come from anyway?)
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