When trying to educate yourself about Australian rockers 5 Seconds of Summer, whether you're a new fan or a journalist writing about them, there are the most basic, basic facts that you need to know: Starting with how three-quarters of the band met at school (Ashton Irwin joined later). And how they were the supporting act for two One Direction tours. And how they have such a love-hate relationship with their single "Don't Stop" to the point where the guys frequently use it to insult each other (not so crucial, but at least it gives you an idea of their sense of humor). And oh yeah, how "5SOS" is not actually pronounced like how you initially think it is. I mean, say "five es oh es" and everyone will know you're a newb. Check yourself, girl: It's pronounced "five sauce." ~themoreyouknow.gif~
Calling 5SOS "five es oh es" is one of those rookie mistakes — one that I admittedly made myself before I got in deep — that just stamps a big ol' "OUT OF TOUCH" right there in the middle of your forehead. So to prevent you from any further embarrassment (and yes, you should be embarrassed), know this: The "SOS" in "5SOS" isn't pronounced like the distress signal. It's pronounced "sauce," like the condiment. For your viewing pleasure, here's a fetus video from 2014 where Luke Hemmings pronounces 5SOS correctly:
And here's a video, compiled by a frustrated fan, that features the correct pronunciation on an endless loop:
As for why it's pronounced that way, I don't think there's any real reason besides that both fans and the band alike just say the acronym like how it's spelled, as opposed to pronouncing each letter. (Personally, it's always reminded me of how "soz" is ~Internet slang~ for "sorry.") Since the guys are obviously the authority when it comes to how they pronounce their own band name, if they pronounce it "five sauce," that means everyone else follows suit. And hell hath no fury like a 5SOS fan trying to figure out why people still say it incorrectly:
5 Seconds of Summer = 5SOS = five sauce. Case closed.