You’re right. Had to dig into my memory for this one and fact check myself.
IRC, BBS, and most forums (of the era) used PM or SP. MUCKs and a few other tools used Whisper. ICQ introduced “IM me”. Part of me remebers using the term “DM” for IRC messages, but I used IRC fairly regularly well into the 2010s.
However, the forum I spent a ton of my younger years on used “Direct Messages” which has likely polluted my memory. Since it was a technology related forum, that was probabaly a customization from the operator to distance everyone from the idea of “private” since everything was clear-text and unencrypted back then. That or I’m confusing “IM me” from the ICQ/AIM/MSN days.
Point being, nobody thought “PM” meant secure and not visible to the server operators back then. It just meant that only you, the recipient, server operators, and 1337 h4xx0rz could see your messages.
What a trip down edited memory lane that was. Thanks for fact checking me.