From the definition: "Its reputation has not risen over the years, and it is still a long way from general acceptance. Use regardless instead." Irregardless is a malapropism, of which the "ir" is superfluous. By the way, we should change this thread to big words we love: mine = superfluous.
I would think the "ir" and "less" negative attachments would basically cancel out and make the work mean "with regard" which is exactly the opposite of how it is used.
I worked for a guy that would say "Let's consolidate this trash". You mean throw it in the dumpsters, right?