the.com/fore

means A shouted warning in golf that a struck ball may be heading toward someone, telling them to watch out or duck.

from Likely a shortening of 'before,' used in the old military sense of warning those standing 'before' — ahead in the line of fire — that something was coming their way; golfers borrowed the same logic for errant shots. The exact leap from battlefield caution to fairway etiquette isn't firmly documented, but the link to 'before' is the accepted root.