When Gaiman was first asked to write a Sandman series, it was intended to be a revival of DC Comics' series from the 1970s. The original Sandman, Wesley Dodds, dated from 1939. A man who used sleeping gas to incapacitate criminals, he left sand at the scene as his calling card.
When it was decided that Gaiman's series would take an entirely new approach, Gaiman's solution to the dilemma of having two Sandmen in the DC universe was to show how Wesley Dodds had been indirectly inspired by the immortal and ancient Sandman, Dream.
Dream's helm was designed to resemble the World War I gas mask Dodds wears to protect him from his own sleeping gas.