Did you know that “no worries” began as an Australianism? From Bryan Garner’s Usage Tip of the Day:
The actor and writer Paul Hogan popularized the phrase outside Australia in his Crocodile Dundee movies (the memorable one of 1986, the less memorable sequel of 1988, and the wholly forgettable second sequel of 2001). Hogan's catchphrase was “No worries, mate.” The wide appeal of those movies made the phrase something of a vogue expression, sometimes with and sometimes without “mate” tacked on the end. . . .I will confess to a sparing use of “no worries” in conversation. (I’ve used the expression twice in these pages, each time in a comment.) But I always thought that “no worries” was a Britishism. And I was unaware of mate . And as must be apparent by now, I’ve never watched a Crocodile Dundee movie.
But beginning about 2000, the expression had spread into mainstream American English without any hint of its foreignness.
But I do subscribe to the Usage Tip of the Day. You can too.
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[I’d like to link to the full explanation, but the Usage Tip of the Day is not published online.]