"Eli5" is 14 characters shorter than "explain like I'm 5".

Yes, except that's not actually what people mean when they type those letters. A five year old has almost zero understanding of math. Where would you even begin?

If you want a simple explanation, just say so. There's really no need to use internet memes for basic communication.

Wow. Based on the responses, you'd think I wrote a style guide that said to use eli5 whenever possible. If you don't like it, don't use it. I don't. I was only pointing out that the abbreviation neither stands for just "explain" nor saves a mere three letters.

I always figured it was supposed to be a single word that started with "eli" followed by 5 letters, in the manner of i18n.

The only English words I could find matching that pattern are elicited, elicitor, elidible, eligible, eligibly, elisions, elitisms and elitists - none of which seem apt, although "elicited" is tantalisingly close. From context I always read it as "elucidate" (elu6?)

So why isn't it Elif?

Because that's what some languages use for else if?

Probably not the real reason...

"explain like I'm 5" is almost certain to be understood regardless of the reader. "Eli5" is unintelligible unless you are part of a particular, narrow, culture. I had no idea what it meant.

(In truth, the "like I'm 5" part is not obvious so could be misunderstood, but is easier to grasp the meaning.)

Ha, I first read the 5 and a capital s.