Here's a snip from the "Jewish World Review" with an explanation of the Dreidel:
Even the custom of playing dreidel, sources explain, is a reminder of the secret of Jewish continuity. The Seleucids had forbidden a number of expressions of Jewish devotion, like the practice of circumcision and the Jewish insistence on personal modesty. They also outlawed the study of Torah, which they rightfully regarded as the engine of Jewish identity and continuity. The spinning toy was a subterfuge adopted by Jews when they were studying Torah in pairs or groups; if they sensed enemy inspectors nearby, they would suddenly take out their dreidles and spin them, masking their study session with an innocuous game of chance.
http://www.jewishworldreview.com/avi/shafran.html
You should try to learn something every day... MW