Perhaps not: the residuum is, you see, Byres, what is left.
-- Frederick Marryat, The Poacher, 1841
Our friend's corporeal envelope had been so well lined with this residuum, as well as various earlier memories of his parents, that their own special Swann had become to my family a complete and living creature...
-- Marcel Proust, translated by C.K. Scott Moncrieff and Terence Kilmartin, Remembrance of Things Past, 1922–1931
Residuum shares a root with the word residue. It comes directly from the Latin residuum meaning "a remainder."