My 90's ISP homepage URL makes more sense. inreach.net/~myusername
Actually, I miss when ISP's all came with some space for simple web hosting. It was a given that a lot of people would want to make their own sites, not just consume them.
Not just Apache, but POSIX shell syntax! It's called Tilde Expansion[0], so in your dash, bash, whatever, ~USER expands to the home directory of USER. This is the general form of standard "bare tilde" syntax as a stand-in for $HOME.