Derivative of the two words, "Jean" and the slang word, "Boner".
A folding of the jeans in the crotch region of a pair of jeans that results in a small to medium sized uprising when worn. Usually found when worn by girls, although they can be found in certain males who either have microscopic genitalia or who wear loose jeans.
Nikki showed me her joner during lunch today, it was quite large. However, mine was larger, so I showed her mine.