Some verbs, in their first person singular form, have an unpronounced '-s' at the end. For example, je suis, je finis, etc. In Latin, the suffix for first person singular was '-o' or '-m': thus sum ...
How does the Latin “SAPIAT” become “sache” [saʃ] in modern French? I thought the reason may be palatalisation as [ʃ] seems to be a palatal sound, but I can't think of any other examples to prove this ...