Possibly the concept existed but the “blameless” term is widely credited to the GP, John Allspaw, who became CTO of Etsy. At least I haven’t found anything definitive predating him.

Also impressive he’s had an HN acct for 12 years but only 5 karma!

The SRE book authors cited the post specifically (https://sre.google/sre-book/bibliography/#All12), and Googlers I’ve spoken to mentioned its influence there.