Although Jack Robinson was well known back then, we know him as quick visiting. Everything else about this man has mysteriously vanished. Some say Jack Robinson is just an imaginary person. There is however, another Robinson behind
Suggestions have been made that John Robinson was the sould background behind the Jack Robinson idiom. In 1660 John Robinson was constable for the tower of London for several years. He is said to be the reason for this saying, because of the way he quickly chopped off people's heads and the ay he quickly let go of the towers inmates. Although this suggestion could be no way possible due to the hundred year difference.
People have their own thoughts and suggestions as to how this idiom came to be. The idiom "Before you can say Jack Robinson" could be used to say something such as, "I'll write this idiom essay before you can say Jack Robinson." In conclusion I suppose we will never really know the true reason behind this idiom. So all I can say is, if you ever have to get something done in a short period of time, just say to yourself, "I can do this before you can say Jack Robinson," and get motivated.