As far as I've been able to make out, it was first proposed as an interview question by Imran Ghory in his blog post Using FizzBuzz to Find Developers who Grok Coding, published on January 24th, 2007.
This was picked up (seemingly on the same day?) by Reginald Braithwaite in his article Don't Overthink FizzBuzz.
A month later (February 26th, 2007), Jeff Atwood would blog about it too, citing the two previous sources in his article Why Can't Programmers.. Program?, and this article is often cited as having popularized the question.
