The Mahometans say that the eating of a melon produces a thousand good works. So named from Melos.
Etre un melon. To be stupid or dull of comprehension. The melon-pumpkin or squash is soft and without heart, hence “être un melon” is to be as soft as a squash. So also “avoir un &cocur; de melon” (or de citrouille) means to have no heart at all. Tertullian says of Marcion, the heresiarch, “he has a pumpkin [peponem ] in the place of a heart [cordis loco ].” It will be remembered that Thersites, the railer, calls the Greeks “pumpkins” (pepones).
Source: Dictionary of Phrase and Fable, E. Cobham Brewer, 1894