从Wikipedia看,Rio Grande是大河的意思,拉美很多水域都以此为名,最有名的是美国和墨西哥之间的Rio Grande。巴西的北大河州和南大河州分别是以两个不同的Rio Grande水域命名的。
Rio Grande do Norte: ... The Vespucci expedition also named the Potengi (Tupi for "River of Shrimps") river, whose considerably large mouth contrasted with the nearby bodies of water, "Rio Grande" (Portuguese for "Great River"), after which the Captaincy, Province, and State were named.
Rio Grande do Sul: ... The coast is one great sand beach, broken only by the outlet of the two lakes, called the Rio Grande, which affords an entrance to navigable inland waters and several ports.
大约就像酒泉有条北大河,信阳有条南大河,两条河没啥关系,和北大、南大也没关系。