Yes it is true. SOme Asutralian people use them need to practice them to understand them. Australian rhyming slang comes from cockney and was brought to Australia by the convicts who first settled the country. They used rhyming slang if they didn’t want others, particularly the authorities, to understand what they were talking about.
Basically, rhyming slang is the use of usually two or more words, the last of which rhymes with the intended word. But there are variations.
Examples
The easiest examples of rhyming slang are straight-out rhymes. Thus plates of meat are feet. And rubbity-dub is pub; depending on context, it could also mean tub as in bath tub.
So ava Captain Cook, for instance, at Captain Cook.
Ava isn’t rhyming slang but simply how some Aussies pronounce Have a as in avagoodweegend (Have a good weekend).
But Captain Cook is definitely rhyming slang and means look.
The variations:
The most common variation is to drop the rhyming word altogether. So you could simply ava captains (have a look) at this example. Sometimes when the rhyming word is dropped, the remaining word takes on a plural form for no logical reason.
A third step is to abbreviate (or corrupt) the first word, so that not only is the rhyming
word gone but the first word in the phrase is corrupted. Hence, seppo for American.
The original phrase is septic tank for Yank and septic is corrupted into seppo. (Don’t ask me why Americans are called Yanks even if they come from the American South.) Another term used is tin tank.
When rhyming slang is flying thick and fast, it’s best to know what some of them mean.