시쳇말 is a combination of two words: 시체 and 말, which are connected with a 사이 시옷 (ㅅ). The 말 part of the word can be translated as "language" or "expression," but what does the 시체 mean? My Korean-English dictionary shows three possible choices: 1) "verse style," 2) "dead body," and 3) "the fashion of the day." In the case of 시쳇말, the third choice is the correct one.
Besides meaning "body," the Chinese character 體 (체) can also mean "form" or "style," so since 時 (시) means "time," the word 시체 (時體) can literally translate as "the time (時) style (體)."
The Korean video below says that 유행어 and 요샛말 are synonyms of 시쳇말 (時體말), but neither 유행어 nor 요샛말 have the "그때" (that time) in their definitions, so to use 유행어 to refer to "past" popular expressions (유행어)," one would have to say, "그때에 유행어."
The reason I am being so picking about the word 시쳇말 is that I recently came across it while reading a book entitled "내 몸 사용설명서" (YOU, The Owner's Manual). Here is the passage to which I am referring:
By the way, what is a 시체양반 (時體兩班)?
ANSWER: It refers to rich, successful businessmen. Already in the Korea of the 1930s, the "new yangban of the time" (시체양반) were the rich capitalists, the people with the money.
In his 1934 novel "고향," the author 이기영 wrote the following: "그는 아주 훌륭한 시체양반이 되였다," which could be translated as, "He has become a respected businessman." In old Korea, businessmen did not get much respect and were not usually called "yangban" (양반).
Finally, in the above video, the word 초주검 is mentioned. Since 초 (初) can mean either "first" or "the beginning" and 주검 means "corpse" or "dead body," the word 초주검 can literally translate as "the beginning of a dead body," implying that a person is near death.
