The Borat video is a complete fabrication. I was tucking in my shirt after taking off the recording equipment.
Quickly tugging your penis to make it semi-erect/chub up usually right before someone sees it.
Person 1: I'm a grower so I had to tuck in my shirt before walking past the pool in my sweatpants.
Person 2: You tuck in too? I do that at the gym!