The name was translated from the Vulcan language and was noted as being a difficult word for a difficult concept. When put simply, it taught to suppress the overt reaction to that which one cannot prevent or remedy. After it had been performed often enough, the exercise became internalized and taught ones control not only over their reactions but the thoughts which might evoke those reactions. This was only the case where the practitioner was incapable of aiding in a situation. However, should they be capable of providing help, than it was expectated that the individual offer service if they were qualified or to get out of the way if they were not. Despite this, it was believed that one was not entitled to overtly display emotion which was capable of disturbing or impeding others in a rescue.
An example of this was when an individual at a mountaintop observed a hovercraft crash into the city where many were killed. The observer should be aware that they did not possess the means to prevent such an incident and thus there was nothing gained by averting their eyes from the deaths or giving into rage or horror. Therefore, if one was alone, they needed to simply yield to their own weakness in doing so but if they were accompanied than what right did they have to add to their companions discomfort by making a display of their own. A simpler version of this discipline was the term Kaiidth.
It took the Vulcan species thousands of years to develop the Mastery of the Unavoidable technique. At some point in the 23rd century, T'Shael attempted to teach this art to Cleante. (TOS novel: Dwellers in the Crucible)