Some foreign-language words were reasonably naturalised to preserve pronunciation — e.g. cañón from Spanish to canyon in English. Other words came into English retaining their original spelling and pronunciation — e.g. noir from French. However, it quickly becomes clear that for other (similar) words different conventions have been employed — e.g. guillotine is spelt the same in French as in English, but the English cognate is pronounced very differently.
Is there any reason for this? Could any such reasoning be additionally applied to derivations like English together from Old English tōgædere?