While Australian English has its own unique characteristics, it is not a derivative of Cockney. The similarities you might perceive are likely due to:
* Shared historical influences: Both Australian and Cockney English have roots in the dialects of England from which their respective speakers emigrated.
* Vowel shifts and pronunciations: Both accents have certain vowel sounds and pronunciations that are different from standard British English. These similarities are due to independent sound changes that occurred in both dialects over time.
* Rhyming slang: Cockney is known for its extensive use of rhyming slang, which is also present in Australian English, though it is not as widespread.
It's important to remember that Australian English is a distinct dialect with its own unique history and development. While it shares some features with other dialects, it is not a direct descendant of Cockney.