An Etymological Dictionary of the German Language/Annotated/Blitz
Blitz, masculine, from the equivalent Middle High German blitze, blicze, blicz, masculine, ‘lightning’ (Swiss even now blitzg for bliktz); a derivative of Middle High German bliczen, ‘to lighten,’ Old High German blëcchazzen (formed like the equivalent Gothic lauhatjun). Allied to the earlier Old High German and Middle High German blic, ‘lightning.’ The Teutonic root blëk corresponds to Aryan bhleg, bhlog, in Greek φλέγω, ‘to burn, blaze,’ φλόξ, ‘flame,’ Sanscrit bhrâj, ‘to radiate, sparkle’ (whence Sanscrit bharga(s), ‘splendour,’ and bhṛgu, ‘the special gods of light’), as well as Latin fulgur, fulmen (for *fulgmen), ‘lightning.’ To the Aryan root bhleg the following also belong: Dutch bliksem, Old Saxon bliksmo, bliksni, ‘lightning,’ Dutch blaken, ‘to flame,’ Anglo-Saxon blœcern, blacern, ‘candlestick’ (see Blaker), and perhaps blank (compare further blecken and Blick).