How did the grapefruit, a hybrid fruit, get its name?

In 1814, naturalist John Lunan published the term grapefruit to describe a similar Jamaican citrus plant. Lunan reported that the name was due to its similarity in taste to the grape (Vitis vinifera). An alternative explanation offered by Tussac (1824) is that this name may allude to clusters of the fruit on the tree, which often appear similar to bunches of grapes.

Grapefruit originated as a natural hybrid. One ancestor of the grapefruit was the Jamaican sweet orange (Citrus sinensis), itself an ancient hybrid of Asian origin; the other was the Indonesian pomelo (C. maxima). Both C. sinensis and C. maxima were present in the West Indies by 1692. One story of the fruit's origin is that a certain "Captain Shaddock" brought pomelo seeds to Jamaica and bred the first fruit, which were then called shaddocks. This apparently referred to a captain who traded in the West Indies in the 17th century. The grapefruit then probably originated as a naturally occurring hybrid between the two plants some time after they had been introduced there.