It’s not unheard of that a shmancy cocktail name may actually have nothing to do with the term itself. From your glass of glistening Grasshopper to a sultry Sex On The Beach, cocktail names have had a notoriously humorous, often ironic, nomenclature history. 

Robert Roy MacGregor was a 17th-century renegade, frequently likened to a Scottish counterpart of Robin Hood. He orchestrated skirmishes against nobility in the Highlands and his posthumous status evolved into that of a legendary folk hero. His renown was so profound that it inspired an operetta, titled Rob Roy, which premiered on Broadway in 1894. Soon enough, New York City resto-bars and pubs witnessed an eponymous cocktail gaining considerable traction among customers. The Rob Roy thus quickly became the distant cousin of The Manhattan, or was even a Manhattan for the Scotch lovers, if you will. 

Containing the primary ingredients of scotch, sweet vermouth, orange zest, aromatic bitters and cherries dunked in brandy, the Rob Roy had indeed become a sensation in the United States soon after its invention. 

The genesis of this cocktail is in the original Waldorf Astoria Hotel. Astoria's position on Fifth Avenue, situated in the lower 30s during the years between 1893 to 1929 played a crucial role in the birth of Rob Roy. This location was conveniently nestled within the vast expanse of the Great White Way, the city's vibrant hub dedicated to the performing arts. Thus, with each theatre production, bars in and around the area would quickly stir up new concoctions and give them catchy names (for example, any favourite character that the audience thoroughly enjoyed). The Rob Roy’s origin story was similar, as claimed by Frank Caiafa, author of The Waldorf Astoria Bar Book.

An indispensable element in preparing the drink is the vermouth. The existence of both Rob Roy and the Manhattan itself owes greatly to the surging popularity of vermouth during that era. Phil Greene, the author of The Manhattan: The Story of the First Modern Cocktail with Recipes, underscores that this is indeed the starting point of such burgeoning experimentations with hard liquor in the States. “Vermouth was an Italian import that no one in America had heard of until it appeared in the melting pot of the cocktail. It’s kind of like St-Germain today. Everyone started using vermouth then.” The latter half of the 19th century witnessed a sharp increase in vermouth-based cocktails among the common folk. 
Close on the heels of the Manhattan’s invention, Rob Roy was introduced to the cocktail universe by 1894. The only difference — scotch came in as a substitute for rye (used in Manhattan).  

Initially, the original proportion of whiskey to vermouth stood at one-to-one. However, with the passage of time and the inclination towards more potent blends, the standard ratio shifted to two-to-one and it remains the same till date. 

Regardless of its origin and creator, the Rob Roy took the American palate by storm, becoming a sought-after drink ordered across the counter. The drink's popularity could be attributed to the familiarity factor associated with Rob Roy’s persona in New York during that era. 

By 1895 then, the November edition of the San Francisco Call was already reporting that a “new cocktail called the ‘Rob Roy’ is excellent.” The recipe soon found its way into cocktail manuals like John Applegreen’s 1899 Barkeeper’s Guide and James C Maloney’s Twentieth Century Guide.