SCDS397 November 2018 TMUX6136
Source off-leakage current is defined as the leakage current that flows into or out of the source pin when the switch is in the off state. This current is denoted by the symbol IS(OFF). Drain off-leakage measurement is not characterization since the drain pin is always connected to one of the two source pins.
The setup used to measure both off-leakage currents is shown in Figure 18