A lot of languages have added support for this over the last few years. It's a nice little quality of life improvement. I use it very regularly now. I find it really handy for currency amounts in cents, so I can say `10_00` for ten dollars, in cents.
Sorry, it's a been feature in a number of languages for decades. Perl has it at least as early as 5.005 in 1998. So naturally, Ruby had it since at least before 1.6 / 2002. Java added it in 2011. It didn't work with Python 2.1 from 2001, but I found it was added relatively late in PEP 515 in 2016 with Python 3.6.
As a latecomer, C23 went with ' just like C++ did almost 10 years earlier with C++14.
