Despite the Dickensian associations with victorian workhouses, Gruel wasn't just for the poor. It was considered healthy and common to eat in society generally.
In the book Emma by Jane Austen, Mr. Woodhouse (Emma's father) is a hypochondriac who eats a diet primarily of gruel.
Mr. Woodhouse was right! Pottage is good, gruel is good. Every time I switch back to eating gruel, my health improves.