A key issue in Moore v. United States is whether income has to be realized to be taxable. An amicus brief in the case was filed by Professors of linguistics who did a 1913 search of the use of the words "income" and "derived" from the Sixteenth Amendment and found that overwhelmingly Americans thought income has to be realized to be taxable. The online dictionary of etymology concurs as follows:
Online Etymological Dictionary:
income (n.)
