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That's a very bizarre change. In 1965 it was determined that the term "yo-yo" was so widely known as a descriptor for that toy that it was considered common speech, and thus the founding company no longer had exclusive rights to the name (founded in 1928): https://en.wikipedia.org/wiki/Yo-yo
Declining sales after the Second World War prompted Duncan to launch a comeback campaign for his trademarked "Yo-Yo" in 1962 with a series of television advertisements. In a trademark case in 1965, a federal court's appeals ruled in favor of the Royal Tops Company, determining that yo-yo had become a part of common speech and that Duncan no longer had exclusive rights to the term.
So Nintendo has literally no reason to fear a lawsuit over the use of the word "yo-yo" in a game made in the 90s. Anyone who tried to sue them over it would be filing an obviously frivolous lawsuit.