Complex sentence: Irregardless is not a word commonly used in place of "regardless" or "irrespective", which has caused controversy since the early twentieth century, though the word appeared in print as early as 1795.
Split into simpler sentences: Irregardless is not a word, yet it is commonly used in place of "regardless" or "irrespective". This has caused controversy since the early twentieth century, although the word appeared in print as early as 1795.