皮肉 is often translated as “sarcasm” or “irony”. Taken literally, it means “skin and meat” and originally comes from an old Buddhism term, 皮肉骨髄 - the extra characters 骨髄 means “bone and marrow”.
In this longer 皮肉骨髄 word, 皮肉 describes the “surface” or “outermost layer” of an idea, and 骨髄 describes the “essential being” or “one’s inner most heart. In the Buddhist world, these two words together means “to understand of the essentials,” i.e. to understand both above and below the surface of an idea.
So if 皮肉 is a metaphor for “surface”, then, 皮肉 by itself acts as a criticism for “not understanding of essentials, and only the superficial.” This is why 皮肉 came to mean “to criticize one’s faults or weak points.” Later it then gained the extra meaning of an unexpected result, or “irony.”
皮肉 is similar to “sarcasm” in the English sense, but slightly different. For example, if your Japanese friend tells you your Japanese is better than Japanese people like a joke, that would be sarcasm - emphasizing a thing by saying the opposite to it. If the Japanese friend instead said “Why don’t you watch more Japanese TV?” in a mean way, this is more like 皮肉. The friend’s suggestion is directly criticizing your Japanese skill, as if to say “You should watch Japanese TV show more because your Japanese is not good.” Take note though: 皮肉 is a negative word, so if the friend was speaking in a generous and kind way, it wouldn’t be 皮肉.
He’s never bothered by hurtful criticisms.
Although she was heathy, my daughter died before me - and I suffer from cancer. It is so ironic (completely unexpected).