acetic (adj.) Look up acetic at Dictionary.com
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" (see acro-).