Comes buche, the enlargement of the esophagus of birds (chickens) and plumas. In the past when someone selling skinny chickens (malnourished) they would make them look fat by feeding them lots of corn (enlarging the buche) and sprinkling cold water on the bird. This would make the bird ruffle her feathers to get warm and thus giving the appearance of being fat a savvy customer would pick up the bird and feel the body. Realizing the scam. He would exclaim ?esta gallina es buche y pluna no más?. A lie, scam, just a show with no substance. Hence anyone claiming to be something (big) but not demonstrating it was called buchipluma.
Used in US as well
"Buchipluma no más eso eres tu, buchipluma no más as the song says"