Sumimasen is one of the most common polite expressions in Japanese, used daily to say excuse me, thank you for your trouble, or I am sorry. The doubled version became popular online as a reaction sound because repetition exaggerates the feeling of flustered politeness familiar from anime and Japanese media. Shared on meme soundboards and in short video edits, it works even for viewers who do not speak Japanese, since tone alone signals an awkward apology, and it remains a quick shorthand for embarrassment.