Originally taken from the word "See you later".
In the Australian way, words get merged into one. Hence the word "Salada" - "See-ya-layta". Also having connection with the brand Salada Biscuits.
Now spelt differently to add emphasis. Salada Biskets is born.
Use of the word has varied and will vary as time goes along.
Currently it is mostly used as a departure saying.
"I'm heading home, Salada biskets."
or
Can be used in a way to describe how drunk you are. "dude, I'm absolutely F*$%&'n Salada biskets, mate."
or
A describing word. "Was that chick hot last night that I danced with?"
Reply "..No she was Salada biskets."