The source of this
synonym for a big win isn"t the slot machine that pays out jackpots. The
metaphor has its origin in the variety of draw poker called "jacks or better,"
in which only a pair of jacks or a better hand can open the betting. Players
ante up into the pot before each deal and it often takes a large number of deals
before one player is dealt a pair of jacks or better hand. By that time the
"progressive jack pot" has mounted to a large sum, or a considerable jackpot,
for the player who wins it. From poker, the word jackpot passed into
general use, first recorded in a non-poker sense in 1884. It was subsequently
used in phrases like to hit the jackpot, "to have great luck," first
recorded in 1944.