The word flatulence didn't always carry such a noxious connotation. It was coined in 1711, but not really, since it's a direct loanword from French flatulence. This is from the Middle French word flatulent (from which we got ours; it's much older than the former), which meant (as today) "affected with gas". This is from the modern Latin word flatulentus, a variation of flatus, a jack-of-all-trades word dealing with air, including definitions such as "blow", "breathe", and "snort". Not necessarily smelly, I might emphasize. One theory traces this to an earlier word, flo, meaning "to breathe or blow". This would be (through Proto-Italic flao) from the reconstructed Proto-Indo-European root bleh, or "to blow". This possibly has connections to another Proto-Indo-European word, bhel, which meant "to swell" and connected to all this since you swell up before blowing out air. What we can see here on a grander picture is that one type of air release became another over time. Fun fact: the word flatulence had a 300% higher usage during 1867 than it does today; it's losing popularity both to euphemisms like passing gas and cruder words like fart, both of which have increased in usage since then.
Adam Aleksic, a rising sophomore studying linguistics and government at Harvard University, has been described as the internet's sixth most famous etymologist. He also has disturbing interests in politics, vexillology, geography, board games, conlanging, and law.