The phrase er det no'n hjemme is everyday Norwegian for asking if anyone is home, with no'n being a spoken shortening people use in casual speech. As a soundboard clip it circulates mainly as a reaction sound rather than a quote from a widely identified film or show. Its six second length gives editors room for the knock or entrance before it and the pause after it. Online it keeps being reused because the meaning is clear from tone alone, so even non Norwegian audiences use it for empty spaces and lonely arrivals.