The story
Han (한) is the Korean reading of the Chinese character 恨, which Mandarin reads as hèn, hatred. Korean kept the hurt and let most of the hate go. The standard dictionary of the National Institute of Korean Language defines it as a heart knotted with deep resentment, a sense of injustice, regret and sorrow: grief that has settled in and will not leave. Koreans say it of a family or a whole people as much as of one person.
You harbour it (han-eul pumda), it forms a knot (han-i maechida), and you release it (han-eul pulda). A father who never got to go to school may call that the han of his life.
How old the idea is remains disputed. The historian Michael Shin calls han modern: it is absent from the first Korean–English dictionary, of 1897, and rare in classical literature. Several scholars trace the image of a sorrowful Korea to the Japanese critic Yanagi Sōetsu, who wrote in 1920 of a 'beauty of sorrow', and date its rise as a national emblem to the 1970s, when minjung theologians and writers made it a badge of shared suffering. Minsoo Kang argues it has faded in South Korea since the late 1990s, while Korean Americans have taken it up.
You hear it in pansori, the old sung storytelling of one singer and a drummer. Late in the twentieth century the sorrowful style won out and pansori came to be called the sound of han, though every surviving epic ends well.