 In 1822, Jacob Grimm put forth the rule in his book "Deutsche Grammatik" and extended it to include standard German.He noticed that there were many words which had different consonants from what his law predicted, and these exceptions defied linguists for a few decades, but they eventually received explanation from Danish linguist Karl Verner in the form of Verner's law.Grimm's law consists of three parts which form consecutive phases in the sense of a chain shift.