An Etymological Dictionary of the German Language/Baum
Baum, m., ‘tree,’ from the equiv. MidHG. and OHG. boum, m.; corresponds to OSax. bôm, Du. boom, AS. beám, m., tree,’ whence E. beam (beam in sunbeam is quite another word; G. Baum is E. tree); E. boom is and Du. bôm, ‘tree.’ The corresponding Goth. bagms and OIc. baðmr have the game phonetic form. The cognates, with Gr. φῦμα, ‘produce,’ are usually derived from the Teut. root bû, Aryan bhû, ‘to become, arise,’ discussed under bauen.