blue balls

Etymology
US English, 1910s,.

Noun

 * 1)  A cramp-like ache in the testicles and prostate region caused by prolonged sexual arousal; testicles experiencing such an ache.
 * 2)  Unfulfilled sexual desire.
 * 3)  Buboes (in a person of any sex) caused by a sexually transmitted infection; the infection that causes them.