'Emptiness' in the Bible

Truly I've been allotted months of emptiness; nights of trouble have been appointed for me.

Let him not trust in a worthless speech. He leads only himself astray, for emptiness will be his reward.

"But hawks and hedgehogs will possess it; owls and ravens will nest in it. God will stretch out over it a measuring line, and chaos, and plumb lines of emptiness, and its nobles.

"I said: "I've labored for nothing. I've exhausted my strength on futility and on emptiness.' Yet surely my recompense is with the LORD, and my reward is with my God.