High Valyrian versus its derivative Low Valyrian dialects

[Anthony Appleyard]

I am reading "A Feast for Crows", and in it I read about the efforts of someone who knew textbook High Valyrian to make himself understood in one of the west Essos ports where the population spoke a derivative of Valyrian. For a real-world analog, compare Classical Latin with very early French as seen (called Gallo-Romance) in the Strasbourg Oaths. https://en.wikipedia.org/wiki/Oaths_of_Strasbourg