the.com/heat stroke

means A dangerous condition where the body overheats past the point its cooling systems can handle, pushing core temperature to levels that damage organs and the brain.

from Straightforward compound English: 'heat' plus 'stroke,' the latter borrowed from the old sense of 'stroke' as a sudden blow or attack — the same sense preserved in 'stroke' as the medical term for a sudden vascular event in the brain. So heat stroke literally means a sudden, violent attack brought on by heat, naming the body's collapse the same way a stroke of lightning or a stroke of bad luck names any abrupt, forceful hit.