It may have well come from a tv show called Kingswood Country, a particularly racist and misogynistic tv show. I expect is also could accept a few other 'ists'. However, it was quite funny in its time.
I am not really sure if the phrase came from the show or was around earlier, the phrase being, Warm the set and cool the tinnies.
I've been known to use the phrase, perhaps after we have been out all day on social matters and it is such a relief to get home and plonk into a chair.
If you know straight away what it means you are probably of a certain age and living in Australia at the time of the tv show. I am just curious as to how widely this would be understood. Perhaps if you do instantly know, hold off to see what others say and then come in later with, I knew that. I'll republish with detail at a later point.
So what does warm the set mean? What does cool the tinnies mean? If you in the US, step up to the plate. UK, step up to the crease.
I just googled the phrase, and it may well have come from somewhere more recent than said tv show.