The case of Grapes and Grapefruit

From:  "Geoffrey Ludwig"

This happens to be the trickiest question. I know grapes and grapefruit are both fruits, right? But why is there a fruit called a grapefruit if grapes is already a fruit? Grapes are berries, and a grapefruit is a citrus fruit. Why is there a citrus fruit called a GRAPEFRUIT if it has nothing to do with GRAPES which is another FRUIT? Who in the world would name a citrus fruit a grapefruit? HUH?

Jennifer emailed us this answer:

It was somebody in Florida many years ago. His daughter pointed at the fruit in the tree and said "grapes" one day, since grapefruit have a tendency to set in clusters of 2,3, 4 fruit. The guy named it grapefruit. That's it; that's the whole stupid story!