bean: [OE] The word bean (Old English bēan) has relatives in several Germanic languages (German bohne, Dutch boon, Swedish böna), pointing to a common West and North Germanic source *baunō, but that is as far back in history as we can pursue it. Beanfeast  apparently derived from the practice of serving bacon and beans (or, according to some, bean geese, a species of goose) at the annual dinners given by firms to their employees in the 19th century. Beano, originally a printers’ abbreviation, appears towards the end of the 19th century.
Old English bean "bean, pea, legume," from Proto-Germanic *bauno (cognates: Old Norse baun, Middle Dutch bone, Dutch boon, Old High German bona, German Bohne), and related to Latin faba "bean;" Greek phakos "lentil;" Albanian bathë "horse-bean;" Old Prussian babo, Russian bob "bean," but the original form is obscure; perhaps from a PIE reduplicated base *bha-bha-
As a metaphor for "something of small value" it is attested from c. 1300. Meaning "head" is U.S. baseball slang c. 1905 (in bean-ball "a pitch thrown at the head"); thus slang verb bean meaning "to hit on the head," attested from 1910.
The notion of lucky or magic beans in English folklore is from the exotic beans or large seeds that wash up occasionally in Cornwall and western Scotland, carried from the Caribbean or South America by the Gulf Stream. They were cherished, believed to ward off the evil eye and aid in childbirth.
Slang bean-counter "accountant" recorded by 1971. To not know beans (American English, 1933) is perhaps from the "of little worth" sense, but may have a connection to colloquial expression recorded around Somerset, to know how many beans make five "be a clever fellow."