I was reading a short story from Chekhov called "Который из трех?" when I came across a hyphenated suffix **-с** attached to certain words. Here are a few examples:

> 
> И при такой самой природе как приятно, знаете **ли-с**, любить такую
>  приятную особу, как вы... Но я несчастлив!
> 
> 
> Очень **несчастлив-с**!
> 
> 
> Ни... **ничего-с**! Я хотел, собственно говоря, вас побеспокоить...
> 
> 
> 

I couldn't find what it means. I even looked through my reference grammar book, but to no avail. I reckon it's either an archaic grammar (the story was published in 1882) or some very obscure one. I would like to know what it means, when is it used and to what sort of words can it be attached?