Honestly, it's just a matter of knowing this list:
- CPU
- RAM
- motherboard
- GPU
- hard drive
- case
- power supply
And roughly how they should fit together.
But every time I build a PC I have to figure out what the latest versions of these parts are, make sure they're compatible, and when I get the parts they might have some unique form factor I have to figure out on the fly. Just going to PC Part Picker and picking out each part is 90% of the way there. After that it's just a matter of getting them, sticking them together, crossing your fingers that it powers on, and installing an OS. If/when it doesn't power on, THAT'S when you start learning...
But I would say building a PC is not a fraction as difficult as say, knowing how to work on a car.
I always assumed it was his nickname from when he worked at the creamery.