An Etymological Dictionary of the German Language/Diele
Diele, f., ‘plank, board,’ from MidHG. dil, dille, f., m., ‘board, partition of boards, boarded floor’ (in LG. ‘vestibule’), OHG. dili, m. (neut.?), dilla, f., with the same meaning. Originally Teut. þeloz, þiliz, n., ‘board,’ was þiljôn, ‘made of boards’; comp. AS. þël, ‘board,’ OIc. þilja, ‘rowing seat’ (Finn. teljo ‘ship's beam, oar-bench,’ comes from Teut.). Comp. further Du. deel, ‘board, floor,’ MidLG. dêle, ‘board.’ Lith. tile, ‘plank of a boat,’ OSlov. tĭlo, ‘ground,’ Sans. tala-m, ‘surface,’ seem to be primit. allied; also Lat. tellus, ‘earth’?.