This method of physical punishment was first invented for disciplinary use on female slaves in Ancient Greece; later this practice traded over to the Roman Empire and was unofficially used as a means of disciplinary punishment and humiliation for female prisoners in the Victorian age. The person subjected to this method was mostly restrained in an immobile position to prevent taking out the root by him or herself, when the sensation became increasingly intolerable.  Nowadays it commonly refers to an according practice in BDSM.
The ginger, skinned and often carved into the shape of a butt plug, causes an intense burning sensation and often intolerable discomfort to the subject. The effect builds up to the maximum within about the first two to five minutes and lasts for about half an hour before gradually easing while the essential oils are depleting. The used ginger can be skinned further or a new one can be used for continuation with an undiminished effect on the subject.
If the person being figged tightens the muscles of the anus, the sensation becomes more intense.
- Lady Green (1998). Kinkycrafts: 99 Do-It-Yourself S/M Toys for the Kinky Handyperson. 206 pages