The term 'Dreidel Letter' refers to the Hebrew letter Gimmel, which is the third letter of the Hebrew alphabet. It is also used in the traditional game of Dreidel, which is a four-sided spinning top with a Hebrew letter on each side. The letter Gimmel is featured on one side of the Dreidel and is associated with the phrase 'Nes Gadol Haya Sham, ' which translates to 'A great miracle happened there.'