Aquiver (adjective): shaking or trembling because of strong emotion; quivering (Merriam-Webster)
Found on Paragraph 5 of “The Story of an Hour”–>“She could see in the open square before her house the tops of trees that were all aquiver with the new spring life.”
I believe the word in this quote means that the trees that Mrs. Mallard was watching from her bedroom window were shaking (excited) to blossom with new leaves.