The raw prawn

There's a saying in Aussie slang: "Don't come the raw prawn", which refers to someone trying to deceive or pull one over on the person shouting about the prawn.

It's really anyone's guess where random sayings like this one come from but there's a theory that it comes down to a raw prawn being wet and slippery, like someone trying to get away with something dodgy. Seems a bit of a stretch, doesn't it?

Can you imagine being on the receiving end the very first time this saying/accusation was voiced? To be in the middle of some kind of confrontation and have someone scream at you about being a raw prawn? I imagine it'd be quite bewildering.

The reason I learnt this today is because it's Australia Day and I spotted this sign outside a fire station.

The meaning of the sign is fairly easily inferred but I Googled it anyway to see what I could learn.

If we accept that being a raw prawn is being deceptive, I'm not immediately sure how it fits with keeping an eye on the barbeque and fire safety.

Unless there's meant to be a joke muddled in there about people cooking raw prawns on their barbies. But why call the chef the raw prawn?

I'm afraid it still doesn't quite connect for me.