Grapefruit was first described in Barbados in the year 1750 under the name "forbidden fruit", but by 1814 it was generally being called "grapefruit." The specific epithet "paradisi" reflects the early name "forbidden fruit." During the first quarter of the 20th century, horticulturists made determined efforts to have the name "pomelo" adopted for this species instead of grapefruit, but by that time the name grapefruit was too familiar to growers and the public. "Pomelo" is still the common name in Brazil. (Citrus Growing in Florida) - Millet

I thought the pomelo was a different species (Citrus maxima)?

In dutch grapefruit is pompelmoes.

What is the difference between a pummelo and a grapefruit?

By: The Citrus Industry, Volume 1
http://www.citrusvariety.ucr.edu/citrus/difference_pumm_grapefruit.html

Pummelos and grapefruit, are of course not the same fruit, the pummelo, is a parent of the grapefruit. - Unfortunately, because the two words "Pummelo" and Pomelo" are so close many people get confused. - Millet