Why is the “Print Screen”-button on keyboards named "Print Screen" when it actually takes a screenshot and copies it to the clipboard?
What is the reason behind it?
Shouldn't it be called “Copy screen”?
Short answer - It was originally used to literally print the screen content.
Wikipedia: Under command-line based operating systems such as MS-DOS, this key causes the contents of the current text mode screen memory buffer to be copied to the standard printer port, usually LPT1. In essence, whatever was currently on the screen when the key was pressed will be printed. Pressing the Ctrl key in combination with Prt Sc turns on and off the "printer echo" feature. When echo is in effect, any conventional text output to the screen will be copied ("echoed") to the printer.
The key needs to have a name to recognize it. And since people are used to it and know what it does, why change it? And "Print Screen" isn't that far away from "Copy Screen" or "Screen shot", so it is still meaningful in some way.
Also it's functionality doesn't have to be bound to screenshots, it can be bound to any function depending on the context. This is why "Copy Screen" could be as inaccurate as "Print Screen" or any other label or icon. Again: The key needs to have a name to recognize it, so think of the label "Print Screen" as a meaningless but recognizable icon.
About the reason we still have this key: Its necessity might be doubtful but it could be missed if it's not there. I think that is why manufacturers are afraid to move away from it.
There's lots of legacy keys on modern keyboards. The original purpose of the Print Screen key was to do as the name suggests - print the contents of your screen to the directly attached printer.
It's a historical thing to save Print Screen - that was how it worked using a printer port in the CLI days. Kinda like how the term "Print to PDF" came about as opposed to "Save as PDF" - a printer driver was used, so it was Print.
"Capture Screen" might be better these days. On mobile devices, it's moot to an extent as a combination of buttons or gestures can be used.