Why do golfers yell this?
No one agrees where this came from.
One story: there was a person that waited down the driving range to see where the ball landed. This caddy was known as a “fore-caddy.” Yelling “Fore!” was a way of warning the fore-caddy that a ball was on the way.
However, there are other origin stories. Here’s a collection.
Why I Looked It Up
I saw a character yell it in a TV show. It’s one of those things that’s natural and known to everyone, but doesn’t really make any sense.