Originally a short, loudmouthed Polish man (first name unknown). Buttinski was famous for giving advice. As a matter of fact, it was rumored (rumoured?) that he was soon to be the royal family's advisor. However, Buttinski's advice soon went too far. In his first week on the job, he convinced Poland to join a war involving three other Europe
an countries. After Poland loss innumerable soldies in said war, Buttinski told the royals that they made a major mistake by joining the war. The queen blew up, demanding that Buttinski be punished. After all, it was Buttinski who recommended joining the war. The king, who was something of a whipping boy, listened to his queen, and ordered Buttinski executed.
After news of Buttinski's execution had spread throughout all of Europe, the nickname "Buttinski" was used to imply that somebody's constant butting in could lead to their downfall. In those days, it was used as a warning.
However, as the 17th century began, Buttinski became more of a sarcastic label. When somebody would enter conversations without permission, they began to get called "Buttinskis" (Buttinskies?). It was used basically to show the meddling person that they were uninvited to a certain conversation.
The meaning is virtually the same nowadays, but friendlier. It still shows the person that they butt in to conversations too often, but it doesn't mean that the person should leave.