'中風' (suffer a sickness caused by 'something' in the wind)-- a term in Traditional Chinese medicine. Traditional Chinese medicine believed that it was a disease syndrome caused by external wind pathogens invading the human body.
Because "wind is invisible, move fast, and unpredictable", many symptoms are classified under '中風', but the most important one has two meanings. One refers to the pathological changes caused by cerebrovascular obstruction and bleeding, that is, Stroke in modern medicine
In the olden time, when someone fell ill suddenly without any apparent cause, people had to blam something invisible. The obvious choices were wind and evil spirit. A stroke had to be caused by something in the wind they thought.
For the same logic, when someone suffered a mental breakdown (發瘋 - get crazy), people might suspect the patient had 揰邪 (ran into an evil spirit)