Meaning

adjective (usually followed by `of') without due thought or consideration

adverb in spite of everything; without regard to drawbacks

originEtymology tree English regard Proto-Indo-European *lewh₁- Proto-Indo-European *lewHs-der. Proto-Germanic *leusaną Proto-Germanic *lausaz Proto-Germanic *-lausaz Proto-West Germanic *-laus Old English -lēas Middle English -les English -less English regardless From regard + -less.

Etymology from Wiktionary, CC BY-SA 3.0