>>88075
4chan's /fit/ board had a thread entitled "That 30-year-old at the gym" about guys in that age range that are clearly anxious about keeping up with men in their 20s, but it eventually devolved into everyone calling each other Boomers.
It spread like the viral cancer it is to other boards and is used to laugh at the habits or foibles that many Millenials are developing as a sign of finally aging since being called a "Boomer" to a lot of Millenials is like calling a Jew a Nazi.
Ex:) >That 31-year-old Boomer who still puts CDs into his laptop to listen to music.