The etymological idea underlying the word soup is that of ‘soaking’. It goes back to an unrecorded post-classical Latin verb suppāre ‘soak’, which was borrowed from the same prehistoric Germanic root (sup-) as produced English sup and supper. From it was derived the noun suppa, which passed into Old French as soupe. This meant both ‘piece of bread soaked in liquid’ and, by extension, ‘broth poured on to bread.’ It was the latter strand of meaning that entered English in the seventeenth century.
Until the arrival of the term soup, such food had been termed broth or pottage. It was customarily served with the meat or vegetables with which it had been made, and (as the derivation of soup suggests) was poured over sops of bread or toast (the ancestors of modern croutons). But coincident with the introduction of the word soup, it began to be fashionable to serve the liquid broth on its own, and in the early eighteenth century it was assuming its present-day role as a first course.
The expression in the soup for ‘in trouble’ originated in the USA in the late nineteenth century.
Subjects: Cookery, Food, and Drink.