A fairy-tale collector found a hidden pattern linking 'father', 'pater' and 'fadar'

Jacob Grimm, better known for collecting fairy tales with his brother, noticed in 1822 that certain consonants shift in predictable ways between related language families: Latin 'p' regularly corresponds to Germanic 'f', for instance. Grimm's Law let linguists reconstruct how languages descended from a common ancestor and diverged over millennia.