A yo-yo, the iconic round children's toy, started out from simple origins. The word as we know it today was copyrighted by Donald F. Duncan in 1933 for the "Flores Yo-yo Company". This copyright moved to Papa's Toy Co. Ltd. when it bought out the former in 1965, but it was later determined that the trademark was improperly issued, so it's fine to use the word now. But where did that come from? The yo-yo as we know it was brought to the United States by Pedro Flores, who was born in the Philippines back when it was a U.S. territory. Thus, we can trace both the yo-yo and its name to the Filipino language of Llokano, where it was yoyo, with a special emphasis on the first o. Since basically all etymologists are only interested in Indo-European languages, we know very little about the semantics and history of this word, but one of the Tagalog (the national language of the Philippines) definitions for the cognate means "toy", so we can reasonably assume that the Filipino languages have this in common, and by extent the Austronesian family in general, though I found a claim that it comes from Chinese. It all comes down to wherever the toy was invented, and historians have found possibilities from Greece to Oceania.
Adam Aleksic, a rising sophomore studying linguistics and government at Harvard University, has been described as the internet's sixth most famous etymologist. He also has disturbing interests in politics, vexillology, geography, board games, conlanging, and law.