Gooch is a term that is used by stupid people who have learned it from the show, "Jackass." As the brilliant people on Jackass were talking about a piercing located between the testicles and anus, the moronic crew referred to it as a "Gooch." That created the obvious chain reaction of every dumb teen and frat boy thinking it was hilarious, and thus referring to it as such. Unfortunately, for these dim-witted neanderthals, it is pronounced, "GEESH" and spelled, "Guiche."
A similar example would be when someone asks, "how long did it take you to gauge that?" You cannot use, "gauge" in this way. The proper term would be, "stretch."
Idiot: "Dude, did you see that photo online? That guy had his gooch pierced."
Intelligent: "That would be a Guiche piercing. It's pronounced, 'GEESH.' 'Gee' sounds like, 'key.' God, I fucking hate you."