An Etymological Dictionary of the German Language/Birke
Birke (Swiss Bilche, Birche), f., ‘birch,’ from the equiv. MidHG. birke (UpG. birche), OHG. bircha, birihha; comp. AS. birce, E. birch; also Du. berk, AS. beorc, OIc. bjǫrk, Goth. *bairka, f., or *bairkjô, f. This term, common to the Teut. group, is one of the few names of trees of primit. Aryan origin (comp. Buche); the pre-Teut. form is bhergâ (bhergyâ) and corresponds to Sans. bhûrja, m., ‘a kind of birch’ (neu. also ‘birch bark’), OSlov. brĕza, f., Lith. bérżas.