What is the X in X-mas?
c.1400, from Old French rivet "nail, rivet," from Old French river "to clench, fix, fasten," possibly from Middle Dutch wriven "turn, grind," related to rive (v.). The English word may be directly from Middle Dutch.
headed pin or bolt used as a permanent fastening in metalwork; for several decades it was indispensable in steel construction. A head is formed on the plain end of the pin by hammering or by direct pressure. Cold riveting is practicable for small rivets of copper, brass, aluminum, iron, or steel, but the larger iron and steel rivets have to be heated to secure rapid and easy closing.