In Big Bang's Global Warning Concert back in 2008, when 'We Belong Together' was being performed, Park Bom was not included and not present at the concert, but instead all Big Bang members participated in the song and made a 'We Belong Together Remix.'

Even though Park Bom was not feautured, G-Dragon sings "Bom, Bom, Bom" at 00:33. It sure sounds like he's saying Bom, but we can not be so sure, right before that it seems like he's also singing "G- G- G-." If he was, that means he was saying 'G-BOM!' Imagine that!

According to Yvonne, she says that Blackjacks says that G-BOM was quite popular back in the day, so it is very possible he was saying Bom's name on purpose since she was not there.

Original post by Chinese ADDICTEDS.
Here's another G-BOM in 2006, observation credit to Yvonne.