You should listen to the http://historyofenglishpodcast.com/ http://historyofenglishpodcast.com/. He goes into great detail about how the Proto-Germanic langua

You should listen to the http://historyofenglishpodcast.com/ http://historyofenglishpodcast.com/. He goes into great detail about how the Proto-Germanic languages evolved via sound changes (e.g. Grimm's law). Also see https://en.wikipedia.org/wiki/Grimm%27s_law https://en.wikipedia.org/wiki/Grimm%27s_law