An Etymological Dictionary of the German Language/Boden
Boden, m., ‘bottom, ground, soil, loft,’ from the equiv. MidHG. boden, bodem, gen. bodemes (the dial. ModHG. bodem is stil used, comp. the proper name Bodmer), OHG. bodam, m., which still exists in the cognate dialects and languages. OHG. bodam points, however, not to Goth. *buþma-, but, with a remarkable irregularity, to *budna-, the corresponding AS. botm, E. bottom, exhibiting a further irregularity in the dental. Goth. *budna- seems probable, since the non-Teut. languages of the Aryan stock point to bhudhmen, bhudhnó- as the stem; Gr. πυθμήν, ὁ (for *φυθμήν, see bieten), ‘bottom’; Lat. fundus (for *fudnus), Sans. budhná- (for *bhudhná-, by the same rule as in Gr.). It is a primit. Aryan word, with the meaning ‘bottom, ground,’ but is not connected, however, with a str. vb. in any Aryan language. — Bodensee obtained its name during the Carolovingian period (formerly Lacus Brigantînus, ‘Lake Constance’) from the imperial palace at Bodema (now Bodmann), which may be the plur. of the subst. Boden.