Solving these block puzzles requires powerful computing power and sophisticated equipment. In return, miners are rewarded with Bitcoin, which is then released into circulation hence the name Bitcoin mining.
https://www.investopedia.com/tech/how-does-bitcoin-mining-work/
I meant the actual word “mining”
Why was it ever referred to as that, who first called it that etc.
Well, if we assume that Nick Szabo released is BitGold whitepaper before Satoshi's Bitcoin whitepaper then I'd credit Szabo. Generally I think it refers to the actual work done by the PoW miner. It's a comparison to the physical power required to mine gold or silver. But that's just me playing the guess game.
"The concept of Proof-of-Work dates back to 1992 when Moni Naor and Cynthia Dwork embarked on a quest to tackle the problem of email spamming. They published an academic journal titled “Pricing via Processing or Combatting Junk Mail.” The concept aimed to discourage spamming by mandating mail senders to perform some computational exercises before sending out an email.
In 1997, Adam Back developed a protocol called Hashcash, a more advanced concept to prevent email spamming. Hashcash itself already included a type of double-spending (peculiar to blockchain technology) by including what is called the “double-spending protection” concept. Interestingly enough, these initial concepts were not referred to as Proof-of-Work themselves.
Szabo first came up with Bit Gold in 1998, though he only fully described it in public in 2005. His proposed digital money scheme consisted of a combination of solutions, some of which were inspired by (or resembled) previous electronic cash concepts.
The first central property of Bit Gold was proof of work, the cryptographic trick utilized by Dr. Adam Back in his "anti-spam currency" Hashcash. Proof of work represented the unforgeable costliness Szabo was looking for, as it required real-world resources – computing power – to produce these proofs."
https://www.realvision.com/blog/what-is-proof-of-work
https://learn.saylor.org/mod/book/view.php?id=30735&chapterid=6704
