According to Wikipedia, the Jamaican tangelo or ugli fruit "was a natural hybrid, having arisen spontaneously like the grapefruit, near Brown's Town, Jamaica, where it is mainly grown today. It was discovered growing wild in or about 1917, then passed through several generations of budwood grafting, selecting for fewer seeds. It was exported to Canada and England by 1934, and to the United States in 1942. UGLI is a registered trademark of Cabel Hall Citrus Limited, under which it markets the fruit, the name being a variation of the word 'ugly', which refers to the fruit's unsightly appearance, with rough, wrinkled, greenish–yellow rind, wrapped loosely around the orange pulpy citrus inside."
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