birchen (not comparable)
From Middle English birchen, birken, from Old English bircen, *biercen, beorcen (“made of birch, birchen”), from Proto-Germanic *birkīnaz (“made of birch”), equivalent to birch + -en. Cognate with Scots birken, birkin (“birchen”), Dutch berken (“birchen”), Low German berken (“birchen”), German birken (“birchen”).