The story
From naph(thalene) + -cillin (“6-aminopenicillanic acid derivative”).
Etymology from Wiktionary, CC BY-SA 4.0.
nafcillin
Today it means: A semisynthetic penicillin that is resistant to beta-lactamase and is used especially in the form of its hydrated sodium salt C₂₁H₂₁N₂NaO₅S·H₂O as an antibiotic. Full definition →