... In Bohemia, Borivor and Ludmilla, the first Christian prince and princess of that duchy, had two grandsons, Boleslav and Vesteslav, or Venceslav, the first a heathen, the latter a Christian.  Boleslav stirred up the pagan population against his brother, and murdered him while praying in church at Prague, on the 28th of September, 644, thus conferring on him the honour of a patron saint and centre of legends.  The House of Luxemburg obtained the kingdom of Bohemia by marriage, and Venceslav was introduced among their appellations in the form of Wenzel; and the crazy and furious Bohemian king of that name sat for a few unhappy years on the imperial throne; but in spite of the odium of that memory, the name of good King Wenceslas, as we call it, held its ground, and contracts into Vacslav and Vaclav.  Some say that it is crown glory, from vienice; others deduce the prefix from vest, the superlative of veliku, great, which furnished the Bulgarian Velika, Veleslav, Velimir. (History of Christian Names, Yonge, 1884)