"The first reported usage of the term was by Rev. Cosmo Lang, Archbishop of Canterbury, part of his 1937 Christmas sermon broadcast on national radio. In an address titled "Christian Responsibility," Lang said:

"Who can think at this present time without a sickening of the heart of the appalling slaughter, the suffering, the manifold misery brought by war to Spain and to China? Who can think without horror of what another widespread war would mean, waged as it would be with all the new weapons of mass destruction?"

http://en.wikipedia.org/wiki/Weapons_of_mass_destruction#WMD_use_and_control)