scatology (n.)youdaoicibaDictYouDict[scatology 词源字典]
"obscene literature," 1876, with -logy "treatise, study" + Greek skat-, stem of skor (genitive skatos) "excrement," from PIE *sker- "excrement, dung" (cognates: Latin stercus "dung"), literally "to cut off;" see shear (v.), and compare shit (v.). Related: Scatological (1886).[scatology etymology, scatology origin, 英语词源]
shit (n.)youdaoicibaDictYouDict
Old English scitte "purging, diarrhea," from source of shit (v.). Sense of "excrement" dates from 1580s (Old English had scytel, Middle English shitel for "dung, excrement;" the usual 14c. noun seems to have been turd). Use for "obnoxious person" is since at least 1508; meaning "misfortune, trouble" is attested from 1937. Shit-faced "drunk" is 1960s student slang; shit list is from 1942. Up shit creek "in trouble" is from 1937 (compare salt river). To not give a shit "not care" is from 1922. Pessimistic expression Same shit different day attested by 1989. Shitticism is Robert Frost's word for scatological writing.
The expression [the shit hits the fan] is related to, and may well derive from, an old joke. A man in a crowded bar needed to defecate but couldn't find a bathroom, so he went upstairs and used a hole in the floor. Returning, he found everyone had gone except the bartender, who was cowering behind the bar. When the man asked what had happened, the bartender replied, 'Where were you when the shit hit the fan?' [Hugh Rawson, "Wicked Words," 1989]