Aquiver (adjective): shaking or trembling because of strong emotion; quivering (Merriam-Webster)
Found on Paragraph 5 of âThe Story of an Hourâ–>âShe could see in the open square before her house the tops of trees that were all aquiver with the new spring life.â
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.