There is the famous בני יששכר where he explains that the four sides of the dreidel represent the four gentile kingdoms of golus. The point represents Klal Yisroel.
נגה”ש is gematriya משיח (as RebE pointed out).
When Moshiach comes, all the nations will recognize that their focal point and foundation is Klal Yisroel.
He also says that there is special significance to a wooden dreidel (gotta go buy myself one!) since it’s connected to the posuk about Moshiach קח לך עץ אחד
(בני יששכר מאמרי חדשי כסלו טבת מאמר ב סוסכ”ה)
I’ve also heard (not sure where this is written) that since on Chanuka the miracle was fully מלמעלה, completely beyond nature – we spin the dreidel from the top. Whereas by Purim the miracle was in a more natural way, מלמטה – so we spin the grager from the bottom.