The word you yell — loudly, immediately — when your ball is flying toward other people. It likely comes from "forecaddie," the person sent ahead to spot balls, warned with a shout of "fore!" A golf ball can arrive at well over 100 mph, so the correct response to hearing it is to turn away, cover your head, and shrink — never look up to find the ball. Not yelling fore on a wayward shot is considered one of golf's genuine etiquette sins.