'nerve-racking' originates from the combination of 'nerve' and 'rack', where 'rack' meant 'to cause pain or stress'.

'nerve-racking' evolved from the older term 'rack', which was used to describe a form of torture, and eventually became a metaphor for causing stress or anxiety.

Initially, it meant 'to cause pain or stress', but over time it evolved into its current meaning of 'causing stress or anxiety'.