via the LA Times (reg. req.),

While playing the Blackhawks on April 29, 1982, in the second game of the conference finals, Canucks Coach Roger Neilson became convinced referee Bob Myers was biased against his team. After yet another call went against the Canucks, Neilson grabbed a white towel, stuck it on the blade of a spare stick and began waving it in mock surrender behind his team’s bench at Chicago Stadium.
Several Canucks players joined him, making their point very clear. Although Neilson was fined $1,000 by the NHL, the towels were a hit back in Vancouver. A local businessman printed up and sold several thousand towels — with the proceeds going to a charity — and fans snapped them up for the next home game. And the next, and the next.