According to the International Genealogical Index, this is an English surname, and one recorded in the spellings of Thornawell, Thorniwell, Thornwell and Thornewell, which may be the only spelling form in use in the 21st century. It is clearly locational and has been recorded in the surviving registers of Greater London since at least the Stuart Period as shown below. However there does not seem to be any place recorded in the gazetters of England in any of the surname spellings, for at least the past two hundred and fifty years. Before that the maps were really too erratic to provide accurate information. It would seem to originate from the pre 7th century words 'torn waella' which literally translate as 'the spring surrounded by thorn bushes,' but may have actually described a defended water hole, where thorn hedges were deliberately grown as a defensive wall to prevent cattle from destroying the place. Some five thousand villages are known to have disappeared since the 12th century, and this is almost certainly another to add to the list. An early example of the surnane recording is that of John Thornwell, a christening witness at St Brides Fleet Street, in the city of London, on September 2nd 1693.