Soup can be traced back to 6,000 BC, but did not yet resemble our broth dish, served with floating vegetables, meats, and pastas. The word "soup" is a derivative of the Vulgar Latin suppa (derived from the Prehistoric Germanic root sup-), which translates to "to soak." Initially, suppa was a bread dish, which had been soaked in broth.
"The bread or toast was, in effect, an alternative to using a spoon...Soups were important in the medieval diet, but the dish that the cook prepared was often a sop that consisted of both nutritious liquid and the means to eat it. The meal at the end of a normal day was always the lighter of the two meals of the day, and the sop appears to have had an important place in it."
And that explains why dinner is commonly called "supper".
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Photo source Wikipedia