The line comes from The Sound of Silence by Simon and Garfunkel, first released in 1964 and later a major hit in its electric version. Its quiet opening, hello darkness, my old friend, has long been recognised far beyond the song itself, and online creators turned it into a shorthand for entering a bleak, awkward or ominous situation. The shortened clip keeps only that entrance, which is why it works so well as a reaction sound. It remains popular because the lyric is instantly recognisable even to viewers who do not know the full song.