Why Is Seltzer “Original”?

I am fond of seltzer, plain carbonated water, rather than the flavored variety. I am been perplexed, however, by the term “original,” which invariable is associated with bottled seltzer. For example, the photo below shows seltzers from three bottlers, each of which contains “original” on the label.

I could have included other seltzers in this picture as well. 

Usually, “original” on a label indicates that a produce was the first of its kind. For example, Hidden Valley markets its Original Ranch salad dressing, which was indeed the first salad dressing of its type. Obviously, however, not every seltzer can be the original one.

I wrote to three companies that market “original” seltzer, asking them about the use of “original.” I received a substantive reply from only one (Canada Dry), and that reply merely referred me to a page on the Canada Dry Web site advertising Canada Dry seltzer. The e-mail message did not really address my question.

Companies marketing “original” seltzer invariable offer flavored products that are basically seltzer with natural flavors and no sweeteners. These products are not labeled “original.” It appears, then, that “original” seltzer is carbonated water lacking other ingredients, although the term “seltzer” (or “Seltzer”) was first applied to naturally carbonated mineral water that contained—not surprisingly—dissolved minerals. In other words, “original” has come to mean “unflavored.” Its use on bottles of carbonated water, however, is misleading, given the usual use of the term.

Does any reader know the origin of “original” as applied to seltzer and how it became universal?