Recall the PIE slide where I discussed the hypothesized mother tongue for English and all Indo-European languages. Why do scholars believe all the languages on the PIE model have a common ancestor? Because their research points to one.
An analysis of sound change is a way to show relationships between languages. Grimm’s Law, named after Jacob Grimm and Rasmus Rask, presents the observation that certain Germanic languages exhibit a common and progressive sound change that isn’t observed in other non-Germanic languages; in particular, stops. This sound change can be observed in Germanic languages consistently over time.
In defining Grimm’s Law in his book, Introduction to Old English, author Peter S. Baker notes, “Perhaps the most important development that distinguishes the Germanic languages from others in the Indo-European family is the one that produced the difference . . . between the p of Latin pater and the f of Old English fæder.” This change, which has come to be called Grimm’s Law, “affected all of the consonants called ‘stops’” (Baker).
As a method to prove relationships, comparative studies look for phonetic and grammatical similarities and these distinct kinds of sound change that take place as a language evolves. If these languages are indeed related, sound change analysis will point to that common PIE ancestor I discussed at the beginning of this section.
So, to recap: Grimm’s law observes that the Germanic language can be shown to share words with other PIE languages; that is, sibling and/or cousin languages of a shared PIE ancestor – meaning the languages have a common etymological origin. These words can be considered cognates; however, cognates can also be a simple result of borrowing words from other languages, which I will discuss next in the ME section of this presentation.