This is from the GNU website, who along with the kernel.org group provide the core O/S software for Linux. Right on their front page, just like kernel.org, they state quote:
The name “GNU” is a recursive acronym for “GNU’s Not Unix”; it is pronounced g-noo, as one syllable with no vowel sound between the g and the n.
So now you take the word of Stallman the crazy communist as authoritative when it suits you. Debate tip: do not completely trash the credibility of someone and then bring him up in an appeal to authority.