DEAD RECKONING ORIGIN

DEAD RECKONING
The phrase to described estimating a course of events or position stems from the sixteenth century when mariners would plot a course based on the last known position, time, compass course and present speed. However this method did not allow for unknown variables such as wind speed and direction, currents and drift. Of course this meant continued use of the process produced cumulative errors.
Originally the method was called ‘deduced’ reckoning which became ‘de’d’, ‘ded, and eventually ‘dead’.