The processus vaginalis (or vaginal process) is an embryonic developmental outpouching of the peritoneum. It is present from around the 12th week of gestation, and commences as a peritoneal outpouching. n males, it precedes the testis in their descent down within the gubernaculum, and closes. This closure (also called fusion) occurs at any point from a few weeks before birth, to a few weeks after birth.
The remaining portion around the testes becomes the tunica vaginalis. And incompletely obliterated remnants of the vaginal process of the peritoneum remaining in the spermatic cord is called the vestige of processus vaginalis.