Definition of "tremblingly"

Andrew, he said, was coming soon. Tremblingly she wondered when, and went to reread Palmer's letter, but though she had hidden it with her father's unread will, both were gone.

1907, Barbara Baynton, edited by Sally Krimmer and Alan Lawson, Human Toll (Portable Australian Authors: Barbara Baynton), St Lucia: University of Queensland Press, published 1980, page 279