The term REUBEN BASE is composed of two words: RYE and RYEBREAD. RYE is a type of grain that is used to make bread, beer, and whiskey. Ryebread is a type of bread made with RYE flour. It is a popular bread in many countries, including Germany, Scandinavia, and the United States. Reuben Base is a combination of RYE and ryebread, which is often used as a base for sandwiches such as the classic Reuben sandwich.