As far as I can tell, the double-x did not infiltrate the English language until the internet went mainstream (Exxon might be the exception—a company name deliberately chosen to be inscrutable and inoffensive). The earliest example I can think of is “anti-vaxx”, as in “anti-vaccine” (see also “antivaxxer”). Then we got “doxxing” (to publish someone’s personal information without their consent). And now we have “looksmaxxing”, which has itself been Watergated (i.e., “maxxing” has become a generic, often humorous suffix to attach to other words, such as “benchmaxxing”).
But where did the OG “anti-vaxx” come from? This 2018 post from Grammarphobia traces the term from its precursors “anti-vac”/“anti-vacc” in the late 19th century all the way to its popularization in the aughts. The Oxford English Dictionary (paywall) dates the earliest known use of the double-x spelling of “vaxxed” to 2004.