(plural staphylococci), 1887, Modern Latin, the genus name, coined (on model of streptococcus) in 1882 by Scottish surgeon and bacteriologist Alexander Ogston (1844-1929). The first element is from Greek staphyle "bunch of grapes," which possibly is from PIE *stabh-, variant of *stebh- "post, stem; to support" (see staff (n.)). The second element is Modern Latin coccus "spherical bacterium," from Greek kokkos "berry, grain" (see cocco-). So called because the bacteria usually bunch together in irregular masses.
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Harper, D. (n.d.). Etymology of staph. Online Etymology Dictionary. Retrieved $(datetime), from https://www.etymonline.com/word/staph