A corruption of the noun, a 'Zohab', which over time has actually developed the direct opposite meaning to the original definition.
This means that a Johab is a word for an extremely small penis, which perhaps goes hand in hand with the inny niplet
1) And so I whipped out my Johab.
2) Suck on my Johab.
3) Caress me, my johab and my inny niplet.