How did the patron saint of Mexico get a name derived from Arabic?
El Moro Judio
You're referring to the Virgin of Guadalupe, the brown-skinned apparition of the Virgin Mary who tradition says appeared before the Aztec peasant Juan Diego in December 1531 just outside modern-day Mexico City. As you correctly noted, Guadalupe's etymological roots spring from Arabic: the name is a mishmash of the Arabic word for valley (wadi) and the Latin lupus (wolf) and was what the Moors called a river in the Extremadura region of Spain. Hernán Cortés and his merry band of murderous Extremadurans venerated a Black Madonna found near their hometown river, so it's no stretch to theorize that any Holy Mother appearing before a bunch of Mexicans on the conquistador's watch would assume the nombre of Guadalupe.
But another school of thought favored by many Mexican and Chicano scholars argues that Guadalupe got Her name thanks to Spanish stupidity. They maintain that Spanish clerics misunderstood Juan Diego when he told them la virgen called Herself Tlecuauhtlapcupeuh ("She who comes flying from the region of light and music and intones a song, like the eagle of fire" in Nahuatl) and Coatlaxopeuh ("I crushed the serpent with my foot"). The two terms are rough homonyms of Guadalupe, goes the tale, and so the Spaniards assumed Juan Diego meant their goddess and renamed his brown virgin Guadalupe. The problem with this revisionist theory, however, is that it has no basis in historical fact. The German theologian Richard Nebel pointed out in his 1992 study Holy Mary Tonantzin Virgin of Guadalupe: Religious Continuity and Transformation in Mexico, "Until today, no one has found any document from the sixteenth century in which one can verify the Nahuatl phonetic origins of the word that the Spaniards supposedly thought resembled 'Guadalupe.'" Besides, the idea of an Islamic-derived Guadalupe is better: imagine how freaked out gabachos will get when they discover that the Empress of the Americas is part Muslim!
I'm a Mexican güero: light-skinned, green-eyed, and blond/brown-haired. I experience more racism from my own people than gabachos. Why so much hate toward Mexican güeros by my darker-skinned raza? Do I remind the pinches indios too much of their Spanish conquerors? Are they just jealous that their horny rucas and sisters keep putting the moves on me? All of the above?
Güero and Loving It!
The only thing Mexicans alternately love and hate more than los Estados Unidos are güero (light-skinned) Mexicans. Blame the Aztecs: when the light-skinned, bearded Spaniards showed up in Mexico in 1519, Moctezuma and amigos thought the conquistadors were manifestations of Quetzalcoatl, a light-skinned, bearded deity that oral tradition promised would return to save mankind in 1519—the very year the Spaniards showed up. The Spaniards quickly put that myth to waste by destroying the Aztec empire, but that initial reverence for güeros seared itself in the Mexican psyche. Light skin became synonymous with power, wealth, destruction. Dark skin meant indio: loser, poor, estúpido enough to believe that marauders were gods. Not even the efforts of Mexican intellectuals during the 1920s to popularize the idea of Mexicans as la raza cósmica (the cosmic race, made up of black, Indian and white blood) could destroy the stranglehold güerismo has on Mexico. That's why you see light-skinned Mexicans on television, in the presidential palaces and in corporate offices. Being a Mexican güero takes you only so far, though, Güero and Loving It: you're still Mexican, after all.