Old English berie, from Proto-Germanic *basjom (cf. Old Norse ber, Middle Dutch bere, German Beere "berry;" Old Saxon winber, Gothic weinabasi "grape"), of unknown origin. This and apple are the only native fruit names.
Our Living Language : Cucumbers and tomatoes aren't usually thought of as berries, but to a botanist they are in fact berries, while strawberries and raspberries are not. In botany, a berry is a fleshy kind of simple fruit consisting of a single ovary that has multiple seeds. Other true berries besides cucumbers and tomatoes are bananas, oranges, grapes, and blueberries. Many fruits that are popularly called berries have a different structure and thus are not true berries. For example, strawberries and raspberries are aggregate fruits, developed from multiple ovaries of a single flower. The mulberry is not a true berry either. It is a multiple fruit, like the pineapple, and is made up of the ovaries of several individual flowers.
[1900s+; perhaps fr the notion of a small unit of something good, and alliterating with buck; see the berries]