I always thought it was the sound of.. erm, flatulence?
Same. We used to say we "farted" when we fizzed.
i need to know about the lore behind mages farting every time they get interrupted casting a spell
When mages are casting spells, they actually eat the reagents, which cause a lot of gas buildup as the mage is casting. If the mage doesn't properly incant and channel the spell, the gas is then expelled from the ass rather than in a spell.
The cost of frequently replacing underwear got so expensive, that our chars just opt to wear the same pair of crusty, ****-stained undies for 25 years instead.
Some
very talented Mages can even incant spells from their ass, like this one. You REALLY don't want to see this mage summon a Daemon...