U.S. name for "para-acetylaminophenol," 1960, composed of syllables from the chemical name: acetyl, a derivative of acetic (q.v.; also see acetylene) + amino- + phenol. In Britain, the same substance is paracetamol.
1808 (in acetic acid), from French acétique "pertaining to vinegar, sour, having the properties of vinegar," from Latin acetum "vinegar" (properly vinum acetum "wine turned sour;" see vinegar), originally past participle of acere "be sharp; be sour" (related to acer "sharp"), from PIE *ak-eto-, suffixed form of root *ak- "be sharp, rise (out) to a point, pierce."
gaseous hydrocarbon, 1860, from French acétylène, coined by French chemist Pierre Eugène Marcellin Berthelot from chemical ending -ene + acetyl, which was coined from acetic + -yl in 1839 by German chemist Justus von Liebig. Liebig's coinage was in reference to a different radical; acetyl was transferred to its current sense in 1850s, but Berthelot's coinage was based on the original use of acetyl.