The term jackpot was first attested in an 1881 edition of the Harvard Lampoon, where it was stylized Jack Pots and described a type of poker game where players needed a Jack card or better to be ante, and a large amount would accrue right before the end. Therefore, the name got applied to a large sum of money; by 1932 it could refer to slot machine winnings and by 1944 it had to do with lotteries too. "Hit the jackpot" was first coined in 1938. Now to break apart the word Jack Pots: the name of the card type Jack comes from Middle English jakke, which only meant "guy", and that goes back to the name John, which I've covered in a previous post. Pot is quite boring: in Old French, it was pot, and earlier in Latin it was pottus. Before that, the etymology is uncertain.
Adam Aleksic, a rising sophomore studying linguistics and government at Harvard University, has been described as the internet's sixth most famous etymologist. He also has disturbing interests in politics, vexillology, geography, board games, conlanging, and law.