"natural or artificial receptacle for holding water or some other fluid," mid-13c., from Old French cisterne "cistern; dungeon, underground prison" (12c., Modern French citerne), from Latin cisterna "underground reservoir for water," from cista "chest, box," from Greek kistē "box, chest" (see chest). Related: Cisternal.
1560s, "an onion," from French bulbe (15c.), from Latin bulbus "bulb, bulbous root, onion," from Greek bolbos "plant with round swelling on underground stem." Extended 1660s to "spherical underground part of an onion, lily, etc." Expanded by 1800 to "swelling in a glass tube" (thermometer bulb, light bulb, etc.).