In J every symbol is precious and extremely well thought out. The ancestor language "APL" uses its own custom symbols where there the traditional Unicode looking division symbol is used. I really like the APL symbols (there's a video of a guy using the special APL typewriter from the 60s on YouTube), but with J you don't have to worry about installing a special font and buying a keyboard with the symbols written on the right keys. J doesn't precede C in age, but the author/architect (Turing award winner Ken Iverson) had been making large contributions to computing well before C, so he would've had no reason to think "let's make sure as many of my symbols follow C as possible". APL and its descendents are used in industry and have been for decades. Primarily in finance (see KxSystem's awesome KDB+ used by many such as Morgan Stanley), but also in places like Volvo...etc.

Edit: I just re-read my comment and I hope it didn't sound too condescending (not my intent). I'm fairly new to J, but it's pretty cool and I hope you give it a shot if you ever need to do any data oriented tasks.

Yes, `%` is division. It's not that odd, if you look at the symbol - it looks quite similar to the division symbol `÷`.

It's almost better asking where C got the idea that it should be mod from!

So where did C get the idea to `%` for mod?

It looks like % has a different use in BCPL, but it's used for mod in B [0], so I'm guessing it's a Thompson/Ritchie invention? (unless it came from some other language that came before B)

[0] https://www.bell-labs.com/usr/dmr/www/btut.html

In APL based languages (like J), the symbol / has a strongly established history of meaning "fold", or, if you prefer, "reduce".

But it is not a "C-based" language. It is APL-based. APL preceded C by at least eight years.