"Strewth" from "God's Truth" Scots/Irish.
"Crikey" a harmless replacement for "Christ" English in its origin.
"Fair Dinkum" = "Straight up" pure Ocker.
"Ocker" = Australian Slang.
Trivia. Paul Hogan's first step to stardom was in cigarette commercials. His catch phrase... "Anyhow, Have a Winfield". Such commercials were known as "Ocker Ads."