Here's a quote from the original use of the term: Overconfidence by the programmer could be attacked by a system that introduced random errors into the program under test.
A similar technique is used routinely by surveillance systems in which an operator is expected to spend eight hours at a stretch looking at a radar screen for very rare events—such as the passing of an unidentified aircraft.
Tests of performance showed that it was necessary to introduce some nonzero rate of occurrence of artificial events in order to keep the operator in a satisfactory state of arousal.
It would give the programmer greatly increased motivation, because he now would know: An early application of bebugging was Harlan Mills's fault seeding approach [1] which was later refined by stratified fault-seeding.
[2] These techniques worked by adding a number of known faults to a software system for the purpose of monitoring the rate of detection and removal.