Origine of OP_RETURN:
Satoshi Nakamoto did not introduce OP_RETURN in the original Bitcoin design.
Here's a detailed breakdown:
1. What is OP_RETURN?
OP_RETURN is an opcode in Bitcoin Script that allows data to be embedded in a transaction in a provably unspendable output.
Any output using OP_RETURN is considered unspendable and is thus not stored in the UTXO set, which helps conserve node resources.
2. When was OP_RETURN introduced?
OP_RETURN was introduced in Bitcoin Core version 0.9.0, which was released in March 2014.
The relevant pull request was merged by Gavin Andresen, who was the lead developer after Satoshi left.
PR: 
3. Why was it introduced?
Before OP_RETURN, users would embed arbitrary data by creating fake outputs using OP_DROP or other hacks, leading to permanent and unnecessary growth of the UTXO set.
OP_RETURN offered a safer and more efficient way to store small pieces of data on-chain.
4. Did Satoshi talk about embedding data?
Satoshi did not encourage embedding arbitrary data in the blockchain.
In fact, Satoshi was concerned about blockchain bloat and believed the blockchain should be kept lean to avoid scaling problems.
He focused on using the blockchain for financial transactions, not as a general-purpose data store.
SO
OP_RETURN was not part of Satoshi’s original Bitcoin design.
It was added by later developers (notably Gavin Andresen) to give a controlled way to embed metadata without polluting the UTXO set.
Satoshi likely would have been cautious or even opposed to widespread arbitrary data use on-chain.
GitHub
Relay OP_RETURN data TxOut as standard transaction type. by jgarzik · Pull Request #2738 · bitcoin/bitcoin
Add new standard transaction type, that permits small amount of data to be attached to a transaction, in the form of an additional TxOut that is pr...
