“Soup to nuts” is an American-English idiom that means “from beginning to end.” It is one of many common English phrases that were coined according to the culinary habits of their particular period. Going by published mentions in the magazines and books of the time, this idiom became prevalent sometime in the 1800s, when meals were elaborate social rituals with a set pattern of courses. People usually began the eating experience with a soup appetizer and ended the meal with a dessert or a drink that contained nuts. Therefore, when someone used this expression, they meant the whole thing.
Although meals have become less formal in the present age, “soup to nuts,” like many outdated English expressions, is still around. Like many such idioms and sayings, it is now used to refer to things other than the original references. It is regularly used these days to describe not just the complete processes of culinary projects, but also the complete processes of projects in business, finance, information technology, engineering and so on; for instance, someone might say “We are undertaking or overseeing everything from soup to nuts.”
It is also used to describe an assortment of things that are being sold. One example would be someone saying that they were selling all parts of something from “soup to nuts.” The expression can be used to denote a group of things that are being classified, like a particular genre.
While the “soup to nuts” expression is relatively modern, these kind of sayings have been around for centuries. “From eggs to apples” is another expression with the same meaning. This expression is derived from the Latin expression ab ovo usque ad mala that appears in the Satires of the Roman writer and poet Quintus Horatius Flaccus, better known to the public as Horace. The Romans apparently started their meals with eggs and finished up with apples. Another expression in the similar vein is “from pottage to cheese.”