bumpkin n.

Old English beam, "living tree," but by late 10c. also "rafter, post, ship's timber," from Proto-Germanic *baumaz "tree" (source also of Old Frisian bam "tree, gallows, beam," Middle Dutch boom, Old High German boum, German Baum "tree," and perhaps also (with unexplained sound changes) Old Norse baðmr, Gothic bagms). This is of uncertain etymology (according to Boutkan probably a substrate word). The shift from *-au- to -ea- is regular in Old English.

The meaning "ray of light" developed in Old English, probably because beam was used by Bede to render Latin columna (lucis), the Biblical "pillar of fire." The meaning "directed flow of radiation" is from 1906. To be on the beam "going in the right direction" (1941) originally was an aviator's term for "to follow the course indicated by a radio beam."

The nautical sense of "one of the horizontal transverse timbers holding a ship together" is from early 13c., hence "greatest breadth of a ship," and slang broad in the beam, by 1894 of ships; of persons, "wide-hipped," by 1938.

*bheuə-, also *bheu-, Proto-Indo-European root meaning "to be, exist, grow."

It forms all or part of: Bauhaus; be; beam; Boer; bondage; boodle; boom (n.1) "long pole;" boor; booth; bound (adj.2) "ready to go;" bower; bowery; build; bumpkin; busk; bustle (v.) "be active;" byre; bylaw; Eisteddfod; Euphues; fiat; forebear; future; husband; imp; Monophysite; neighbor; neophyte; phyletic; phylo-; phylum; phylogeny; physic; physico-; physics; physio-; physique; -phyte; phyto-; symphysis.

It is the hypothetical source of/evidence for its existence is provided by: Sanskrit bhavah "becoming," bhavati "becomes, happens," bhumih "earth, world;" Greek phyein "to bring forth, make grow," phytos, phyton "a plant," physis "growth, nature," phylon "tribe, class, race," phyle "tribe, clan;" Old English beon "be, exist, come to be, become, happen;" Old Church Slavonic byti "be," Greek phu- "become," Old Irish bi'u "I am," Lithuanian būti "to be," Russian byt' "to be."