I first came across ぼんぼん in “Art of Fighting 2” (Original Title: 龍虎の拳2). More specifically, in Ryou Sakazaki’s (リョウ・サカザキ) ending. In that ending, his friend and rival Robert Garcia (ロバート・ガルシア) comes to congratulate Ryou for winning the King of Fighters tournament. Then Robert reveals that he used the prize money to pay off loans and debts, and he presents Ryou his share, which is 500 yen (In case you’re wondering, 500 yen is 4.57 US dollars as of this writing). Ryou, not surprisingly, is greatly offended by this, and gets into a fight with Robert. During their punching and kicking, Robert says this:
I think it translates to this: I’m this rich green young man from a well-to-do family, annnnd-!
Robert speaks the Kansai dialect, and ぼんぼん is spelled in katakana, for reasons that are not clear to me.
ぼんぼん has the meaning of “green young man from a well-to-do family”, but that’s a bit of mouthful, don’t you think?
Is there an equivalent term to ぼんぼん in English?
Alright, it turns out that I got the translation wrong. Apparently, a more accurate translation would be “You rich silver spooner-!” It's a good thing there are people who can clear these things up!