This comes from Hebrew. It is a proverb that means "Things don't always happen as they are supposed to be".
"Supposed" in Hebrew is "AMUR". this is also a name for the fish "Ctenopharyngodon idella"
To pretend you have to leave early just to get rid of annoying person in the pub. Upon leaving the pub, make sure all your friends go in one direction and the annoying person in the other. When he/she is out of sight, it's safe to go back in a have a good time with your friends!