Boo-urns
A word orginating from Waylen Smithers in the episode of The Simpsons entitled A Star is Burns. Mr Smithers informs Mr Burns the crowd is not saying Boo Burns but Boo Urns.

Boo Urns thus is an alternative to saying Boo, if you wish to Boo someone or something without them actually knowing
me :That last customer was very boo-urns

me: Wolverine was so shite, Deadpool was only in it for 10 minutes

you: BOO-URNS!!!! BOO-URNS!!!

me : I have to finnsh work an hour later

you: That's freaking boo-urns we we're gonna go to the movies.