I am always fascinated by the multiple relationships between language and society, especially when I am confronted with expressions that are not self-explanatory. And when it comes to pee, English offers some mysterious examples. For examples, if you are angry or disappointed, you are also pissed. And if you are pissed, there is a high chance that you will send other people away, letting them know that they should piss off. Why is this?
No clear explanation exists. Some people claim it is just because of the link to dirtiness which adds a negative connotation to the expression, thus reinforcing its strength. In Italian, people do not refer to pee, but angrily invite the other person to “go shit”. Scatological words, just as swear words, help people find a way to release stress, anger, pain or emotionality in general. Such words are still part of our taboos, and this makes them perfect to create vulgar expressions. By saying them, we overcome a limit and feel somewhat released.
Alternatively, there is a more literal explanation: indeed, it is possible to imagine that one gets irritated if hit right in the centre by a bucket of pee. In the Middle Ages it was common practice to collect the night excrements in a bucket and empty this latter on the street the next morning. I guess, getting soaked in urine is not the best experience ever.
However, another version circulates regarding the birth of the phraseology “to piss off”. As a matter of fact, it is also claimed that the expression started becoming popular during the years of World War II. The story goes that the dog of general Eisenhower peed on a map and the officers joked, saying that the enemy was pissed off.