1930s. From social + fascism, ultimately after Russian social-fašizm (1930 or earlier; frequently attributed to G. E. Zinoviev, Soviet politician, but the use by him has not been traced, although he did express the idea that ‘social democracy has become a wing of fascism’ as early as June 1924, during the Fifth Congress of the Comintern). Compare German Sozialfaschismus.