Grimm's Law, as enunciated by J. L. Grimm, is the law regulating the interchange of mute consonants in languages of Aryan origin, aspirates, flats, and sharps in the classical languages corresponding respectively to flats, sharps, and aspirates in Low German, and to sharps, aspirates, and flats in High German tongues.
Definition taken from The Nuttall Encyclopædia, edited by the Reverend James Wood (1907)
Grimm, Wilhelm Karl * Grimsby