It’s been around a while: the Oxford English Dictionary quotes a citation from Indiana that appeared in Harold Wentworth’s American Dialect Dictionary of 1912. And it turns up even in the better newspapers from time to time: as here from the New York Times of 8 February 1993: “Irregardless of the benefit to children from what he calls his ‘crusade to rescue American education,’ his own political miscalculations and sometimes deliberate artlessness have greatly contributed to his present difficulties”.
Professor Laurence Horn of Yale University points out, the duplication of negative affixes is actually quite common in English. Few users query words such as debone and unravel because they are so familiar. In earlier times there were even more such words, many recorded from the sixteenth and seventeenth centuries: unboundless, undauntless, uneffectless, unfathomless and many others.
Thanks for the post.