From Wikipedia:

Its name is derived from the wrist-motion of a skilled user of a mandoline, which resembles that of a player of the musical instrument mandolin.

I'm visualizing two restaurant prep cooks who've just returned from a tobacco-free smoke break. One begins to energetically chop carrots using this thing which, as yet, has no name. The other looks at him and says, "Dude! It looks like you're playing a mandolin! Can you play "Whiskey Before Breakfast" on that thing?"