Grimm’s Law

A law discovered by Jacob L. Grimm, the German philologist, to show how the mute consonants interchange as corresponding words occur in different branches of the Aʹryan family of languages. Thus, what is p in Greek, Latin, or Sanskrit becomes f in Gothic, and b or f in the Old High German; what is t in Greek, Latin, or Sanskrit becomes th in Gothic, and d in Old High German; etc. Thus changing p into f, and t into th, “pater” becomes “father.”