The phrase became popular online as a Vietnam War meme, built on the idea that American soldiers could not see enemies hidden in dense jungle. Posts paired the line with images of empty forests, bushes, and trees that suddenly felt hostile. As it spread through gaming clips, image macros, and short videos, the wording settled into variants like the trees are speaking Vietnamese. That history explains its lasting use as shorthand for a hidden threat, especially in shooter games and edits where someone is waiting unseen to strike.