Why do people swear, and what does taboo language actually do?
Because swearing is not processed like ordinary vocabulary. It recruits emotional and automatic systems rather than the ordinary language pathway, which is why it behaves differently from every other kind of word.
The neurological evidence, which is unusually clear. People with severe aphasia — unable to produce ordinary speech after left-hemisphere damage — frequently retain fluent swearing. People with Tourette's may produce involuntary taboo speech. This indicates that swearing is substantially supported by subcortical and right-hemisphere structures associated with emotion and automatic vocalisation, rather than by the left-hemisphere language network.
What it actually does:
Pain tolerance. Experiments repeatedly find that swearing aloud lets people keep a hand in ice water longer than repeating a neutral word — an effect attributed to stress-induced analgesia. The effect diminishes in habitual heavy swearers, which is a nice demonstration that the power depends on the taboo remaining intact.
Emotional discharge, which is the everyday function: a pressure valve after injury or frustration.
Social bonding. In many groups, swearing signals intimacy and lack of pretence — permission to be informal — and the ability to swear with someone is a marker of closeness.
Emphasis and credibility, since it signals genuine feeling.
Aggression, which is the use everyone notices and a minority of actual use.
Where taboos come from, and they shift. Historically English taboos moved from religious profanity to bodily and sexual terms, and more recently the strongest taboos attach to slurs targeting groups — which is a meaningful change, because those words cause harm to identifiable people rather than merely breaching decorum.
The persistent myth that swearing indicates a limited vocabulary is not supported: people who produce more taboo words in a timed task tend to produce more words overall.
Second-language swearing feels weaker, because the emotional weight was never attached — which is why people find it easier to swear in a learned language.