An Etymological Dictionary of the German Language/Blitz
Blitz, m., from the equiv. MidHG. blitze, blicze, blicz, m., ‘lightning’ (Swiss even now blitzg for bliktz); a derivative of MidHG. bliczen, ‘to lighten,’ OHG. blëcchazzen (formed like the equiv. Goth. lauhatjun). Allied to the earlier OHG. and MidHG. blic, ‘lightning.’ The Teut. root blëk corresponds to Aryan bhleg, bhlog, in Gr. φλέγω, ‘to burn, blaze,’ φλόξ, ‘flame,’ Sans. bhrâj, ‘to radiate, sparkle’ (whence Sans. bharga(s), ‘splendour,’ and bhṛgu, ‘the special gods of light’), as well as Lat. fulgur, fulmen (for *fulgmen), ‘lightning.’ To the Aryan root bhleg the following also belong: Du. bliksem, OSax. bliksmo, bliksni, ‘lightning,’ Du. blaken, ‘to flame,’ AS. blœcern, blacern, ‘candlestick’ (see Blaker), and perhaps blank (comp. further blecken and Blick).