What is the story behind "Get off my lawn"? [closed]

It's an American phrase and comes from the idea of a retired old man who takes excellent care of his front yard or lawn: mowing it often, no weeds, trimming the edges. Kids, sometimes accompanied by dogs, may want to run through it or play on it, which can damage it. So the old man shakes his fist or cane at the kids saying, "Get off my lawn!" He's often also upset at "excessive" noise, or any noise from children really!

It sounds like the usage you're hearing is that of very experienced people who are cranky at being told something they already know. In essence, they want younger/newer people to respect their knowledge and experience. They may also resent someone newer working on projects or systems that they consider their domain/area of expertise.