Reese Witherspoon says she doesn't quite know how her youngest son came up with his nickname for her. In a social media post Wednesday, Witherspoon revealed her 12-year-old son Tennessee Toth calls her "Morty." The actress shared the video as part of a social media trend revealing what the people in her life call her.

Reese Witherspoon jumped in on the fun on May 7, posting a lighthearted video on Instagram where she listed the different names people call her. And while most of them make total sense, one in particular had me doing a double take.