“Pluma” is actually the word for feather in Castellano but also came to refer to the writing instrument made from such plumage (ostrich being highly sought, I understand). Thus a “plumista” was one who sold pens.
I suppose that means the plumista sold what could be sort of a dual use item…by day, a solid tool of documentation and work…by night, a flexible tool of seduction. Today, “bolígrafo”, or “boli” for short, is now a more common term for the ubiquitous ball point pen–much less romantic, no?
Just one of a million shards of the Barcelona of old you can find as you wander the city.