I believe it was coined on MadTV. There was a sketch involving the "birth control pilgrim" (played by Will Sasso) who prevented pregnancy by screaming colonial-era warnings detailing what would happen should intercourse ensue. The final portion of the sketch involved Michael McDonald masturbating to a porno video. The pilgrim tells Michael to "unhand thy giggle stick" or something like that, and when he doesn't, the pilgrim shoots him with a tiny musket:

"Ow, my giggle stick!" -Michael McDonald