When a person is rejected by the person they love, they masturbate to thoughts and past experiences of the person they love.
The origin of the word is believed to have come from the Aztec Empire, where males, when rejected, would sit down in public and uzjaru.
Person 1: "Will you marry me?"
Person 2: "No" - Person 2 proceeds to run away
Person 1: " Well, time to uzjaru"