Blam!
From Halopedia, the Halo wiki
Blam! was the code-name for Halo: Combat Evolved, before it came out. It was used because the original name, "Monkey Nuts," couldn't be spoken to Jason's mother. So, it was switched to "Blam!" Blam! is now used to bleep out curse words on the Bungie forum. Most likely as a tribute to the word itself.