Well, it just so happens that I bumped into an article from a 1983 issue of American Speech where the answer was to be found (please don’t ask how I seemed to be randomly browsing such an esoteric journal).
Philip Kolin says: The coinage mocktail appears for the first time, I believe, in an advertisement for Libbey Glass in Food Service Marketing (Feb. 1979, p. 76). According to that ad, mocktails “are a relatively new group of beverages prepared without any alcohol whatsoever.” Kolin comments that the ad was for a new line of mocktail glassware (I had no idea that glassware was so specialized – perhaps because most of mine was purchased at Ikea).
He further states, clearly with the air of someone who loves language: Mocktail is a clever invention. It humorously rhymes with cocktail, but has a semantically appropriate first syllable. Mocktails are literally mock cocktails, with the sense of mock in mock chicken or mock turtle soup. The -tail of the second syllable of mocktail, however, has acquired a new meaning-that of the unshortened (and unadulterated) cocktail.
If the term mocktail has only been around since the late 1970s, what about the term cocktail? Well according to a Wikipedia article, the term cocktail first appeared in print in 1806 where it was described as a ” stimulating liquor composed of spirits of any kind, sugar, water, and bitters — it is vulgarly called a bittered sling and is supposed to be an excellent electioneering potion, in a smuch as it renders the heart stout and bold, at the same time that it fuddles the head.”
Just a little etymology to end you week.
Reference: Kolin, P.C. (1983). Mocktails, Anyone? American Speech, 58(2): 190-191.
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