1704, "of or pertaining to the use of fire" (a sense now obsolete); 1825, "of or pertaining to fireworks and the art of making them," from pyrotechny "the manufacture and use of gunpowder" (1570s), from pyro- "fire" + Latinized form of Greek tekhnē "art" (see techno-).
Figurative use, "brilliant, explosive display," is attested from 1847. Related: Pyrotechnical (1610s, from pyrotechny).
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/pyrotechnics">Etymology of pyrotechnics by etymonline</a>
Harper, D. (n.d.). Etymology of pyrotechnics. Online Etymology Dictionary. Retrieved $(datetime), from https://www.etymonline.com/word/pyrotechnics