It was 'blow off' when I was at school. Was never mentioned at home.
Now it is fart and little dd says fart too, 'I done a fart mummy.' I can't stand any of the twee euphemisms. I'd feel embarassed to say them.
Now we live in the north, people around us say 'pumped.' or 'poomped' as it sounds like to me.
How can 'farting' be common, I think tweeness is a bit lowbrow myself. Fart is a verb in german isn't it, meaning 'to go.'