In the 16th Amendment the phrase "from whatever source derived":

The 16th Amendment was specifically designed to remove the Court's objection to taxing dividends from (federally-connected) stocks and interest from (federally-connected) bonds. The court regarded stocks and bonds, and the dividends and interest from them as property. To tax them would require a direct tax, which the income tax is not.

The 16th Amendment severed the link between that source and the income from it. Any income (derived from the exercise of federal privilege of course) could now be taxed without regard to its source, property or not.

Many people read the 16th Amendment and immediately conclude that "from whatever source derived" means that all their earnings are subject to a tax. That is clearly not what the 16th Amendment means. A "source" is a category such as property or services, and does not determine whether your earnings are derived from a federally-connected activity.