Source code
Discussion
What was that unit referred to as in the code? And if there isn’t a name for it in the code, who suggested using “Satoshis” or “sats”?
Read the white paper and Banking on Bitcoin is a good documentary on YouTube. Keep in mind it is old and much has changed such as the introduction of the lightning network. The Book of Satoshi has almost all the email correspondence with Satoshi. https://bitcoin.org/en/bitcoin-paper