It's interesting you say that. I've searched for origins of Satoshi's code many times in the past, thinking if I could just find that one time he reused an old piece of code, I could retrace some of his footsteps to better understand his thought process. I was never successful. Of course, it's entirely possible I was just looking in all the wrong places.
If you searching just on the Internet then you are missing around 50 years of history of networking and software in general.
I'm not sure if it is practical for you, but a lot of information is available in printed magazines, but not in their official "articles", but in the "classified ads" and other cheap less-than-full-page advertisements. Researching those would be extremely time consuming, even if you can find the library that has those magazines undamaged with all pages available.
One more avenue for search is to look at the nearby code, not just strictly IRC-related. There were multiple methods used to discover node's own external IPv4 address. Those also aren't all invented by Satoshi, but borrowed/copied from the pre-existing code. Those were the other things that tended to trigger false-positives.
Are you a CS history researcher associated with an accredited university? Because if you are really into history of CS I may be able to put you in touch with people who may be willing to donate their personal archives fairly soon. But you would really need to be able to read obsolete media like open-reel magnetic tapes or U-Matic and SVHS video cassettes with PAL/SECAM color.