From grape + fruit, an allusion to the grapelike clusters of fruit on the tree. Ciardi proposes another theory. The pummelo's botanical name was Citrus grandis, meaning "great citrus [fruit]", due to the large size of the fruits. It would be natural to call the new pummelo variety a "greatfruit". By saying that name a few times, with its consonant cluster, it sounds like "grapefruit", and it would easily have morphed to that form. This second suggestion is completely speculative, without attestation, but seems much more reasonable than the equally speculative "grape cluster" theory. Actually, pummelo fruits do not not grow in grapelike clusters.
Derived terms 
- Grapefruit on Wikipedia.Wikipedia
- Citrus paradisi on Wikispecies. Wikispecies: Citrus paradisi
- Category:Citrus paradisi on Wikimedia Commons. Wikimedia Commons: Category:Citrus paradisi
- Category:Grapefruits on Wikimedia Commons. Wikimedia Commons: Category:Grapefruits
Borrowed from English.
- grapefruit: the tree of the species Citrus paradisi
- grapefruit: the fruit produced by the tree of the species Citrus paradisi