Where Does Bricking It Come from?

Bricking it is derived from shitting a brick, meaning being very afraid.

What does the British saying bricking it mean?

To be very scared. Ex: He didn't do very well in the interview – we felt a bit sorry for him as he was clearly bricking it. Origin: When you're so scared that you shit bricks.

What does it mean if you're bricking it?

slang To be very scared or nervous. (A reference to the more vulgar phrase "shitting bricks.") Of course I was bricking it when I woke up to the sounds of an intruder in my house! My brother is so strong and scary-looking that you'll be bricking it when he threatens you.