You see, you have to have tongs to bring the leafy goodness from salad bowl to plate. There is, in fact, no such thing as a tong. A pair of tongs is "an instrument with two movable arms that are joined at one end, used for picking up and holding things."
Tongs, like scissors, come only in pairs. Alone, each arm or blade is fairly useless. There are many other nouns that only appear in the plural, such as grits. A local radio spot for McDonald's touted the chain's breakfast offerings, including one that came with "a hash brown." Apparently, at least one copywriter here can conceive of such a thing, but I confess I'm stumped as to what would constitute one hash brown.
I suspect that advertising genius may once have written fashion copy. After years of crafting beautiful descriptions of the latest style of "pant" or "jean," naturally she lost her judgment in a sea of singularity. Having worn away her innate sense of the two-by-two nature of pants, she could look at sauteed shredded potatoes and see a "brown." Thank goodness McDonald's doesn't serve grits.