The shape is an arc, starting fairly thin at the bottom, increasing in thickness as the arc circles clockwise to the 2 o'clock position. It represents a swirl or spin.
This icon is used for washers and dryers. A spinning top shape was considered but it would require exploring the entire shape to understand the meaning and even then it may not be relatable. The curved line is more representative of spin. I suspect the change in thickness may not add to the tactile meaning but may improve visual meaning. Also design decisions were made to separate it from the moon tactile icon.