Smallswords, why the terms pillow and mourning swords?

[corrado26]

I red these posts with great attention because I have in my collection a small sword totally blackened and I didn't know what could have been the reason for this surface treating. On the blade there is a portrait or perhaps a caricature of a person whose meaning is also unknown to me. The sword has a length of 880mm and a total weight of 295g what is very light.
It could be French as well as English.
Thanks for comments
corrado26