degrimm1-8, Exercise 2: Grimm's law

Model answer (check the examples with a linguistics reference):

Grimm's law describes a regular set of sound changes that happened as the Germanic languages split from other Indo-European ones. A "p" sound in languages such as Latin or Greek often corresponds to an "f" in Germanic, and a "t" to a "th".

Two pairs: Latin pater and English father (p to f); Latin tres and English three (t to th).

It is called a law because the correspondences are regular, not random: the same change applies across many words, with a smaller number of exceptions that later scholars explained. The idea that sound change follows rules was a key step in historical linguistics (check the role of Rasmus Rask and later refinements such as Verner's law).

It has no connection with the fairy tales.