Jack Robinson (mythical person)
Jack Robinson is a name present in a common figure of speech used to indicate a period of time, typically in a sarcastic manner. The normal usage is, "(something is done) faster than you can say Jack Robinson" or otherwise "before you can say Jack Robinson." The phrase can be traced back to the 1700s.
According to Grose's Classical Dictionary, published in 1785, the reference is to an individual whose social visits were so short that he would be departing almost before his arrival was announced. 
Several other explanations have been cited:
- Supposedly, an English gentleman of the early 19th century named Jack Robinson was a person who changed his mind. A person had to be quick to catch him in a decision.
- Between 1660 and 1679 the officer commanding the Tower of London was one Sir John Robinson. It may be that the speed of beheading with an axe may be the basis, Jack being a diminutive form of John.
- Another version is that Sir John (Jack) Robinson, the Constable of the Tower of London, held at the same time a judiciary appointment in the nearby City of London, and could and did condemn a felon in the City, then have him transported to the Tower where he commanded the execution, the whole process being done 'faster than you can say Jack Robinson'.
- John Robinson (1727–1802) was Joint Secretary to the Treasury from 1770 to 1782 and regularly acted as a Government Whip, responsible for organising elections and political patronage; of his reputation for political fixing, Nathaniel Wraxall wrote that "No man in the House knew so much of its original composition, the means by which every individual attained his seat, and, in many instances, how far and through what channels he might prove accessible." Therefore fixing something "faster than you can say 'Jack Robinson'" was very fast indeed.