Example of lateral thinking puzzle..
When the British army first introduced metal helmets, the number of soldiers requiring treatment for head injury rose sharply. Why was this?
The metal helmets were probably introduced because warfare had become a little more 'violent'. Therefore, injuries to the head, and elsewhere, would increase anyway.
Ludwig's question is discussed here. An interesting observation is...Was the increase in injuries after the introduction of steel helmets due to an increase in the number of troops at the front line?
'Lateral Thinking' has always been around. (Think how the punch-lines of so many jokes depend on it !). But Edward de Bono was the one credited with applying the name to the process. Have a look here