spherical-shaped bacteria, plural of Latin coccus (attested from 1883 as a bacterium name), from Greek kokkos "berry" (see cocco-).
antibiotic drug, 1944, from Modern Latin Streptomyces, genus name of the bacterium from which the antibiotic was obtained, from strepto- "twisted" + -mycin, element used in forming names of substances obtained from fungi. First isolated by U.S. microbiologist Selman Abraham Waksman (1888-1973) and others.
popular name for a bacterium or other extremely small living being, 1878, from French microbe, "badly coined ... by Sédillot" [Weekley] in 1878 from Latinized form of Greek mikros "small" (see micro-) + bios "life" (from PIE root *gwei- "to live"). Intended to mean literally "a small living being," the use of bios is incorrect, as in modern science generally (see bio-); in Greek the compound would mean "short-lived."
1847, plural of Modern Latin bacterium, from Greek bakterion "small staff," diminutive of baktron "stick, rod, staff, cudgel." So called because the first ones observed were rod-shaped. Introduced as a scientific word 1838 by German naturalist Christian Gottfried Ehrenberg. A classical plural sometimes also erroneously used as a singular.
The Greek word is from a PIE *bak- "staff used for support, peg" (compare Latin baculum "rod, walking stick;" Irish bacc, Welsh bach "hook, crooked staff;" Middle Dutch pegel "peg, pin, bolt"). De Vaan writes, "Since *b was very rare in PIE, and Celtic shows an unexplained geminate, we are probably dealing with a loanword from an unidentified source."