The noun anguish refers to severe physical or emotional pain or distress. A trip to the dentist might cause a cavity-prone person a lot of anguish.
We get this word from a Latin word, angustus, which literally meant "narrow" but developed the figurative sense of "distressed" — think of being choked off or forced into a small space. In modern times anguish has been in the English with the parallel and related meanings of "physical torment" and "emotional suffering." Both kinds might be experienced at the hands of a dentist who likes to make his patients squirm in agony.