"Just beneath the navel-like opening in the blossom end of each navel orange, there is a small and, more or less, fetal orange, usually having five or six pithy segments. The navel strain that we know now originated in Bahia, Brazil, probably as a bud sport, or mutation, of the Brazilian Selecta Orange. In 1870, an American Presbyterian missionary in Bahia was impressed b the seedlessness and rich flavor of this unusual orange with an umbilicus at its blossom end, and sent twelve nurser-size trees to the United States Department of Agriculture in Washington. The department propagated the trees and sent the progeny to anyone who cared to give them a try. In 1873, Mrs. Luther C. Tibbets of Riverside, California, wrote for a pair of trees, got them, and planted them in her yard. Mrs. Tibbets' trees caught the attention of her neighbors and, eventually, of the world. From them have descended virtually every naval orange grown anywhere on earth today." ~ from Oranges by John McPhee
From "swag" to "on fleek," tweens explain the changing English language.