Douglas Harper's Etymology Dictionary
Usage examples of "flash-point".
Not only was it an ugly scene, it was one that looked as if it would only require one single flash-point to trigger off a near riot, to convert their vengeful emotions towards Johnny Harlow into physical action against him and this, it was clear, was the apprehension that was uppermost in the minds of the police, for they moved in close to afford Harlow such protection as he might require.