From ThoughtCo: The term GRAWLIX refers to the series of typographical symbols (such as @#$%&!) used in cartoons and comic strips to represent swear words. The plural is “grawlixes.”
Also known as “jarns,” “nittles,” and “obscenicons,” grawlixes usually appear in maledicta balloons alongside the comic characters who are uttering the oaths.
The term GRAWLIX was introduced by American comic artist Mort Walker (creator of Beetle Bailey) in the article “Let’s Get Down to Grawlixes” (1964) and revisited in his book The Lexicon of Comicana (1980).
The symbols that work best for the grawlix are those that fill up space: @, #, $, %, and &. Hyphens, plus signs, asterisks, and carets (^) leave too much white space within the body of the grawlix for it to look like a single word. The standard recommended grawlix is: @#$%&. This uses the five beefiest symbols in the order they appear on an American keyboard. (If you curse with a British accent, try @#£%&.)
Because it represents words spoken in anger or excitement, the grawlix should always end with an exclamation mark, even if it’s an interrogativegrawlix: @#$%&?! Finally, you should reserve your use of the grawlix for casual writing and close friends; the grawlix is inappropriate for professional writing.