Background: The informant learned this word from the internet. It was prevalent on the internet around 2018. It was the acronym of “仔细想想，非常恐怖。” Variations include alternating the order of the characters.

Context: The phrase is often used to describe a scenario or concept that seems innocuous or even mundane at first glance, but upon closer examination or reflection, it reveals itself to be much more sinister or alarming than people would have initially thought. The informant saw an internet post saying, “the brain is your most important organ—that’s what your brain told you.” People commented on the post with the main piece.

Main Piece:
细思极恐
[something] contemplated carefully and becomes very scary

Analysis
This phrase emerged when the Chinese internet created a lot of acronyms for daily use. The fact that these acronyms are all four characters might be influenced by Chinese Chengyu- an idiomatic expression, most of which consists of four characters and has a story behind it. The Chengyu is from historical or legendary stories and fables. The modern four-character phrases can be applied to a variety of contexts, such as political situations, social issues, or personal experiences, just like what people used to do with Chengyu. The main piece could be a continuation of a long tradition as a result of the habits of the Chinese language.