Most people who hear or use this expression understand it to be the Australian way of saying “don’t worry about that.” It is said to be an Australian’s way to “represent a feeling of friendliness, good humor, optimism, and ‘mate ship’.” It has been called the national motto of Australia. However, I found one dark reference asking that the term not be used. Nazi death squads said “Keine Sorge” or Keine Angst” (no worries) to Ukrainians just before executing them. That’s just one more thing to justify  residual anger toward the Nazis, and I’m certain I will enjoy hearing “no worries” in the future.