The story
Became famous in the 1925 coalminers' strike in New Waterford, Nova Scotia, Canada, when J E McClurg, vice-president of BESCO, intent on starving the strikers into submission, was heard laughing at the strikers, saying "They can't stand the gaff." It then became an expression of defiance for the miners.
Etymology from Wiktionary, CC BY-SA 4.0.