Antibiotic
Etymology
From Greek "anti-" (against) and "biotikos" (pertaining to life), from "bios" (life) — literally "against life." Popularized by microbiologist Selman Waksman in the 1940s for compounds that one microorganism makes to destroy another.
noun · /an-tih-by-OT-ik/
A drug that kills bacteria or stops them from multiplying.
What it names
Use it precisely for the anti-bacterial medicine — not a catch-all for anything that fights infection.
Example
Antibiotics do nothing against a cold, because a cold is caused by a virus, not bacteria.
Related idea
An antibiotic targets bacteria; an antiviral targets viruses — and neither works on the other, which is why demanding antibiotics for a viral illness only breeds resistance. An antibody, by contrast, isn’t a drug at all but a protein your own body makes.