Donald F. Duncan, Inc. had registered “Yo-Yo” as a trademark on January 24, 1933, and spent the next three decades suing anyone who put the word on a competing toy. In 1965, the Seventh Circuit Court of Appeals threw that protection out entirely, ruling in Donald F. Duncan, Inc. v. Royal Tops Manufacturing Co. that “yo-yo” belonged to the English language, not to Duncan’s company. The evidence that sank the trademark came largely from Duncan’s own files: a 1931 statement the company itself had filed with the Patent Office, years before it ever tried to claim the word as exclusive property.

A Word Duncan Didn’t Invent

The court found that “yo-yo” was a Malayo-Polynesian term originating in the Philippines, where it had already functioned as the toy’s generic name for years before Duncan trademarked it, according to the appellate record hosted by Justia. A 1916 Scientific American article describing the toy in general use throughout the islands became part of the evidentiary record, alongside expert linguistic testimony from Dr. Henry Lee Smith on the word’s foreign etymology. Perhaps most damaging, Duncan’s own 1931 filing with the Patent Office had acknowledged that “yo-yo” meant “come back” or “springy” in Philippine languages, and openly questioned whether the term alone could ever be held as anything but descriptive.

Duncan Didn’t Even Coin the Trademark Himself

Duncan’s own predecessor hadn’t been first to register the word, either. A company called Flores Yo-Yo Corporation had registered “Flores Yo-Yo” as a trademark on July 22, 1930, and when Duncan’s side later tried to register “Yo-Yo” on its own, the application was rejected because of that existing registration, according to the opinion hosted by Justia. Duncan’s company got around the problem by acquiring the Flores registration by purchase, then used that acquired trademark as the foundation for the exclusive rights it spent the next three decades enforcing against everyone else in the yo-yo business, including, eventually, its own former employee.

Duncan Built the Market With Filipino Demonstrators

Duncan’s predecessor company had employed Filipino performers to demonstrate the toy in American storefronts starting around 1931, according to the same court record, and one of those early demonstrators, Joseph Radovan, worked for Duncan until 1937, when he quit to form the company that would eventually become Royal Tops — the very rival Duncan was now suing nearly three decades later. The court also noted that Duncan’s own advertising had worked against the trademark for years. The company’s slogan, “If It Isn’t a Duncan, It Isn’t a Yo-Yo,” used “yo-yo” as the generic name for the toy category rather than as a brand name, reinforcing exactly the public usage Duncan was now asking a federal court to prohibit, according to the opinion as separately archived by CourtListener.

Trying to Take the Word Back — and Spending a Fortune Doing It

By the mid-1950s Duncan appeared to sense the danger. The company began pushing “return top” as an alternative term and, according to the court’s findings, was spending roughly $1 million a year on advertising by 1962 and 1963 trying to make it stick. The effort came too late and cost too much relative to what it bought: the court read Duncan’s own pivot toward “return top” as evidence the company already understood “yo-yo” had slipped into public domain, undermining its own infringement case in the process. Duncan also tried to rely on a 1955 license agreement and consent decree with Royal to argue the genericness question was already settled, but the court rejected that too, finding the 1955 deal itself had been obtained through Duncan’s failure to disclose an existing 1948 license it held with Marx.

A Trademark Lost to Its Own Success

The Seventh Circuit reversed the judgment that had favored Duncan below and sent the case back down, effectively stripping “Yo-Yo” of trademark protection nationwide and leaving every manufacturer free to use the word on packaging without licensing it from anyone, according to Justia’s record of the ruling. A companion claim over the “Butterfly” trademark also failed for lack of evidence. Duncan hadn’t lost the case because a rival outmarketed it. It lost because it had marketed too well for too long — the word became so synonymous with the object that American shoppers stopped hearing it as a company name at all, and no amount of Patent Office paperwork could put that back in the bottle once the public had already decided otherwise.