The Nuttall Encyclopedia
Increase in the value of land or any property without expenditure of any kind on the part of the proprietor.
Wood, James, ed. Entry for 'Unearned Increment'. The Nuttall Encyclopedia. https://www.studylight.org/encyclopedias/eng/nut/u/unearned-increment.html. Frederick Warne & Co Ltd. London. 1900.