This is slang, modern internet slang, as you’re probably aware. I’ve been aware of it now for a few months, so that means it’s probably about three or four years old. And already out of date.
You also probably know that flex in this context means boast. Until very recently though, I’d assumed it meant fetish.
In retrospect, yes, it seems a little odd for me to presume that, and it seems really obvious that it actually means boast. It did make sense in context though.
Usually when the expression’s used, it’s in reply to someone boasting about something unusual. And I guess I latched onto that unusual part. I took it to mean that the person saying Weird flex, but OK was indicating that they think it’s weird that the boaster had such an interest in something so strange. An interest so strong, in something so strange, that it was like a fetish.
And when it was explained to me that flex means boast, of course it made perfect sense. I was even able to figure out all by myself that it referred to metaphorically flexing muscles. Still though, I like to think that I was kind of right. They’re basically the same thing really, aren’t they?
Not fetishes and boasting in general of course, but in these cases. Whether flex is meant as boast or fetish, what’s still being pointed out is how unusual the person’s area of interest is: That’s an odd thing to show off, or That’s an odd thing to fetishise. Not that different, are they?
Of course these mistakes are going to happen when you try to figure out slang from context, instead of looking it up. And I don’t mind, because that’s the kind of intellectual exercise I enjoy. Weird flex, but OK….