casque (n.)

"water-tight, barrel-like vessel for containing liquids," mid-15c., from French casque "a cask; a helmet," from Spanish casco "skull; wine-vat; helmet," originally "potsherd," from cascar "to break up," from Vulgar Latin *quassicare, frequentative of Latin quassare "to shake, shatter" (see quash). The sense evolution is uncertain.