Without a list, we can't be sure how narrowly you want the explanation to be tailored. What I think you're talking about is probably universal in language, and isn't a feature of language per se, it's a cultural one, manifested in language. Farting is deemed to be socially negative, so the term "fart" is one of those dis-preferred words, and instead to use some euphemistic replacement, like "poot" (but that's child language) or "flatulate" (rather medical sounding), or "pass gas". There are numerous other examples referring to body parts and actions, also ethnicity. What's on the list and which list it's on varies over time, as does the most likely referent, for example "breast" was for a while a less-polite term. Ethnic terms seem to be particular volatile, no doubt because the underlying social issues change rapidly.
The same phenomenon exists is every language that I know of. For example, in Logoori polite speech in the presence of elders, you should use the verb "breathe" to refer to farting; the singular of "buttock" (cheeks) is used to refer to the anus; there are various insulting ethnic terms which of course you don't use in the presence of members of that ethnicity (words which meant things like "foreigner", "mud-person", "bush savage", "despised"). On the other pole of word-tabooing, a number of languages have special rules about men saying words that contain sounds from their mother in law's name, such as "hlonipha" in Nguni society. In Javanese, there are at least three speech registers, depending on one's relationship to the interlocutor, which involves different lexical items and different grammatical constructions.
The simplest albeit most risky way to determine that there really are such conventions is to try violating the apparent conventions, and see what the effect is.