With the passion of a thousand suns do grammarians hate irregardless. Grammar forums are rife with rage at its continued existence. It’s called an “evil word“, “a corruption, an abomination“. Richard Lederer wrote, “Of all the misuses that slither through the English language, irregardless will get you into the hottest of water.” You can even buy a T-shirt advertising your low opinion of irregardless.
The question isn’t whether or not irregardless is a word, because that’s such an ill-defined question. Of course it’s a word, as it’s a string of letters with a fairly well-agreed-upon intended meaning, a string that is standardly separated from other words in a sentence by spaces. But asking if it’s a word isn’t the question anyone’s interested in; when people ask if irregardless is a word, they really mean to ask if irregardless is a valid and well-accepted component of Standard English. And on that front, as with many words that I use, such as jaggerbush or slippy, the answer is no, it’s definitely non-standard. The reason why is obvious; it’s got a morphological double negative, with the negative prefix ir- and the negative suffix -less. As a result, it doesn’t fit the (singularly negative) meaning it’s intended to convey.
Irregardless appears to have arisen as a blend of the two standard words irrespective and regardless, and it’s not new. The American Dialect Dictionary antedates it to 1912. Thanks to Google Books, I can even offer a few unconfirmed earlier occurrences for irregardless:
(1) “[...] B. Gosse Esq., of London, who gave indiscriminately to every object irregardless of worthiness, and disliked to destroy anything.”
[Nature's Revelations of Character, by Joseph Simms, MD, 1873]
(2) “Individually, at least, I am in favor of the education of whole country, irregardless of race, color, or previous condition.”
[Transcript of the Congressional Testimony of William H. Hill, December 28, 1876]
(3) “[...] an agreement amongst everybody who handles coal in the New England cities to protect themselves irregardless of the situation and irregardless of the demands of the people [...]“
[Court Proceedings from 1906]
Honestly, these early attestations surprised me. I’d figured, as I assume most people do, that irregardless was a fairly new phenomenon. I was wrong; not only is irregardless over a century old, but it’s even appeared in older formal writing, such as the official text of the U.K. Contagious Disease Act (Horned Cattle) of 1880. As I found out while trawling the Oxford English Dictionary, I oughtn’t to have been so surprised by the long pedigree. In fact, irregardless would have fit in just fine in the 16th and 17th centuries:
“[un-] is sometimes redundantly prefixed to adjectives ending in -less. [...] The type, however, chiefly belongs to the later 16th and 17th centuries; among the instance from that period are unboundless, uncomfortless, undauntless [...]“
Note that for these double negative words, like with irregardless, the intended meaning is negative. It might sound crazy that this could ever have been a common and productive pattern, but here’s an example from a 1570 poem:
“Who seeking Christ to kill, the King of everlasting life,
Destroyed the infants young, a beast unmerciless,”
How about that? I suppose it’s not overly surprising that this is the case; the 16th and 17th centuries were a time when double negatives were still being used to indicate negation. Shakespeare, who wrote in this period, used them as negatives. And unmerciless and irregardless are just instances of double negatives within a word.
Even knowing all that, it’s still kind of surprising to me that irregardless is isn’t so much an ill-formed word as it is a latecomer who missed its chance by a few centuries. That doesn’t mean I’d advise using irregardless; far too much has changed in the language since 1570 for irregardless to be valid in Modern English. It’s just neat that something that’s now so anathema used to be acceptable.