Much like a butt dial, this happens by accident and often the caller is unaware of having done so. The nut dial is typical in two situations:
1. Phone in front pants pocket and catches nut shift.
2. Phone resting on car seat between legs and gets sack dragged.
Dude, I think you butt dialed me yesterday. I finally hung up.
Nah man, I probably nut dialed you. I had my phone on the seat while we were offroading.