Karl Verner
Verner’s best contribution to linguistics is nowadays known as Verner’s Law. This law explains certain sound changes in the Germanic languages. The Proto-Indo-European voiceless stops became voiced stops or fricatives in Proto-Germanic. In order to even discover the principles of this law, Verner had to study other Indo-European languages. This principle was a major contribution to the understanding of sound change and the reconstruction of Proto-Indo-European, the hypothetical ancestor of the Indo-European languages.