Groin pad
From wipipedia.org
A groin pad is a piece of padding that may be worn over the male genitals to increase the size of the wearer's male bulge. It may be incorporated into a garment such as a Speedos-type swimsuit, thong, posing pouch or jockstrap, or be loose and held in place by a tight garment.
A groin guard is sometimes also referred to as a groin pad.