> 
> Austin had distanced himself and his colonists from American filibusters in dramatic and determined fashion, but the sad escapade set a-rattling
>  the sabers of many a newspaper editor in the United States and many a political firebrand in Mexico.
> 
> 
> 

I can understand the sentence, but why the author uses *set a-rattling the sabers of*. I've googled and searched it in corpora, yet nothing comes up. Is anyone know similar sentences or something about it?