The phrase “hand in the cookie jar” refers to being observed or apprehended for a theft of money or other valuable items from the rightful owner who is unaware of the fact that he or she is the victim of theft.
Although there is no exact date for when people began to keep money and valuables in cookie jars, the phrase became popular in America during World War II.
The term “cookie jar accounting” was coined in the late 90s in America and pertains to a certain business practice of storing up profits from good years to create a reserve which can be used to increase profits in bad years.
As technology continues to advance, the cookie jar on a computer is an area of memory set aside for storing digital cookies. Programs can detect specific information by searching the contents of the jar. If this is done without the consent of the owner of the computer by unauthorized individuals or businesses and it is traced back to the individual or the business, the individual or business has been caught with his/her/their “hand in the cookie jar.”
This sort of illegal behaviour may lead to serious criminal charges or it could lead to nothing more than a slap on the wrist.
Historically Speaking 