However, I think I have found what you might be looking for:
The Index of Coincidence is a measure of the probability of two randomly selected letters being the same in a piece of text. It was first described by William Friedman and his wife Elizabeth in the 1920s. index of pirates 2005
Many "Index of 2005" searches are performed by netizens trying to find old, lost software or "abandonware" from that specific year. However, I think I have found what you