I have enjoyed having Shabbat lunch by many types of Jews, Ashkenazik, Sefardic, Hassidic, and many variations of the above. One thing I have seen in common, despite many variations of customs, is Cholent. How did it become so widespread that Jews of heralding from myriad countries all decided to eat hot stew on Shabbat morning? Why is it not eaten on Friday night as well?