I'll bare my arse in Fenwicks' window
A northern swear word that means you’re so confident something won’t happen, you’d rather flash your backside in a fancy shop window than be wrong.
I’ll bare my arse in Fenwicks’ window if this cake doesn’t come out perfect.
She said she’d bare her arse in Fenwicks’ window if he didn’t call her by the end of the week.
He promised he’d bare his arse in Fenwicks’ window if the printer didn’t work.