"armor for the head, helmet," 1570s, from French casque "a helmet," from Italian casco, from Spanish casco "a helmet; a skull" (see cask).
Entries linking to casque
cask 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.