Douglas Harper's Etymology Dictionary
aceto-
before vowels acet-, word-forming element from comb. form of acetic and generally indicating compounds from or related to acetic acid.
Wiktionary
aceto-
pre. 1 (label en organic chemistry) Containing a methyl group bonded to a carboxyl group. 2 (label en organic chemistry) Containing a methyl group bonded to a carbonyl group. e.g. (term: acetophenone)