The term is a reference to the TV show where the lead character is trapped in time and travels therein by leaping into the body of someone in the past, but having no idea who he is or why he is there. In order to leave the body, the lead character must figure out what "situation/conflict" must be resolved or wrong must be righted by the host body. The people around him assume he is the person whose body he occupies, so anything he does, the people around him think it is the host body doing it.
Pressured to prove his theories or lose funding, Dr. Beckett prematurely stepped into the Project Accelerator, and vanished......
He awoke to find himself trapped in the past, suffering from partial amnesia and facing a mirror image that was not his own.
Fortunately, contact with his own time was maintained through brain wave transmissions with Al, the Project Observer who appeared in the form of a hologram that only Dr. Beckett can see and hear.
Trapped in the past, Dr. Beckett finds himself leaping from life to life, putting things right that once went wrong, and hoping each time that his next leap will be the leap home..........
-- Sam Beckett, "Genesis"
The Gutenberg press, an invention featuring moveable type, represented a quantum leap forward for people in the 15th century.
Email represented a quantum leap forward in productivity in the 1990s.