'Grahamy' - when something is "nearly, but not quite."
This originates from the mid 80's when my best friend was going out with a guy named Graham. He was mediumly good looking but really had absolutely nothing between his ears and his bright blue eyes always had an absent look to them. One day he told us he had applied to be a model. Once he'd left to go home someone in the room just commented that modelwise he was "so nearly, but not quite!"
A few months later we were in a supermarket where we couldn't read the language on any labels and my friend bought a fizzy drink with pictures of unrecognisable fruit on it. When she had her first sip she commented "hmmm...very Grahamy". I had a sip and understood exactly what she meant as it was a coconut water and lychee drink that could have been so nice but it didn't taste as good as it looked on the label! After that the word Grahamy has always stuck.
Another one is 'Robert Barr' - this comes from the local Sheffield word 'Bobbar' which means that something is rubbish or useless but can also mean shit so is also seen as a sort of childlike swearword. Robert Barr is used in the presence of very young children that won't connect the fact that Bobbar is actually being said so they won't pick it up!
Finally a word I say all the time as my swear word! 'Piggin' 'eck'. I was brought up not to swear and therefore I had to invent something that I would automatically come out with if I accidentally dropped something on my toe or hurt myself in front of other people!