early 13c., "an act or expression of disapproval, rebuke, etc., for something deemed wrong;" mid-14c., "responsibility for something that is wrong, culpability," from Old French blasme "blame, reproach; condemnation," a back-formation from blasmer "to rebuke" (see blame (v.)).
word-forming element meaning "lacking, cannot be, does not," from Old English -leas, from leas "free (from), devoid (of), false, feigned," from Proto-Germanic *lausaz (cognates: Dutch -loos, German -los "-less," Old Norse lauss "loose, free, vacant, dissolute," Middle Dutch los, German los "loose, free," Gothic laus "empty, vain"), from PIE root *leu- "to loosen, divide, cut apart." Related to loose and lease.
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<a href="https://www.etymonline.com/word/blameless">Etymology of blameless by etymonline</a>
Harper, D. (n.d.). Etymology of blameless. Online Etymology Dictionary. Retrieved $(datetime), from https://www.etymonline.com/word/blameless