The original idea behind someone with longhorns on their vehicle was that it represented a person who was in the oil business. Back when the oil business first started, a large portion of the land used for drilling had cattle on it. By putting horns on the truck, the thought was that the bull in the pasture would leave the truck alone thinking it was a bigger bull. Didn't work well but a tradition was born. Needless to say, others picked up the idea and now it just represents someone who had nothing better to do one day than put some fiberglass horns on their car.
Still not sure where the idea of a bull scrotum came from. I do know that my BIL just HAD to have a set and then was too embarrassed to put them on his truck and drive on a road. He put them on his ATV instead. I probably shouldn't have bought him a pair of pink ones and gotten blue ones instead
