c. 1600, "pertaining to hearing or sound," from French acoustique, from Latinized form of Greek akoustikos "pertaining to hearing," from akoustos "heard, audible," verbal adjective from akouein "to hear," which probably is from copulative prefix a- (see a- (3)) + koein "to mark, perceive, hear" (from PIE root *kous- "to hear," which is also the presumed source of English hear).
In reference to material meant to deaden sound, 1924. Of sound reproduced mechanically (rather than electrically) from 1932 in reference to gramophone players; acoustic guitar (as distinguished from electric) is attested by 1958. Related: Acoustical; acoustically.
in the names of sciences or disciplines (acoustics, aerobics, economics, etc.), a 16c. revival of the classical custom of using the neuter plural of adjectives with Greek -ikos "pertaining to" (see -ic) to mean "matters relevant to" and also as the titles of treatises about them. Subject matters that acquired their English names before c. 1500, however, tend to be singular in form (arithmetic, logic, magic, music, rhetoric). The grammatical number of words in -ics (mathematics is/mathematics are) is a confused question.
<a href="https://www.etymonline.com/word/acoustics">Etymology of acoustics by etymonline</a>
Harper, D. (n.d.). Etymology of acoustics. Online Etymology Dictionary. Retrieved $(datetime), from https://www.etymonline.com/word/acoustics