You've probably heard "okay boomer" from the know-nothing generation who can't even properly define the term (in a minor example, the Mike Stoklasa-William Shatner "boomer fight" is between a Greatest Generation member and Gen-X). It's the same vein as "cool story, bro" which by the way they hate having used against them.
You might also know Boomer as a character on Battlestar Galactica. In the original series, he was the black guy with the...well, booming...voice. In the remake, the character was now a woman, and an asian, and ultimately a Cylon (warning: the proceeding is a spoiler), played by Grace Park (no relation to Linda, and a member of the infamous NXIVM cult that was a major thing in the Canadian media landscape a few years ago which I could have sworn I had written about but I guess not).
That remake, helmed by former Deep Space Nine writer Ronald D. Moore (last seen 'round these parts missing a golden opportunity to retcon replicators), ran in the early to mid-2000s. This interview from 2003, just before Battlestar Galactica's remake would air, featured the following exchange:
IGNFF: What was the dynamic you were looking for in that?MOORE: It started from the relationship between that character and the chief mechanic & the crew chief, Tyrol. At first Boomer was a man, in my head, and the crew chief was going to be a woman, and there was something about the power relationship that I didn't want to play that's it's the officer man and the enlisted woman. It just felt too boss and secretary. That's a caricature, because it's obviously not, but I wanted it to be a forbidden romance. I wanted it to be something that two people were doing outside the norms, and that would give us sort of, "Why don't officers and enlisted mix? What are the problems with having men and women in the military, serving together?" I wanted that relationship to deliver that, and I thought it was more unusual to give the woman the senior role and the man the supporting role. And then I just called her Boomer because why not? There was a Boomer character, and I didn't have a role for another pilot so "Okay, Boomer."
Wait...did Ron Moore create the term? Admittedly the context was different (apparently 2009 was the first "dismissing a more experienced person sharing their experience" use), but it certainly is a shock to see somebody in 2003 casually drop "okay boomer" into a conversation as a linguistic shortcut.
