The origin of the Kray Family name is by no means clear, there are several possibilities, including the Old English word “Cray” for a stream, common still in place names in Kent, as in Crayford, St Paul’s Cray, St Mary’s Cray etc (and of course in “Cray-fish”), if this is the name’s derivation then the family would have been initially from Kent before moving to the more industrialised areas surrounding the south eastern flanks of London, or across the river Thames to Essex and from there into London. However is rare for the name to be spelled with a K rather than a C, so the proof that it originated as a Kentish name is not conclusive.
There are two other possibilities for the name. One is that the name could be contraction of McCrae or McKray, dropping the “Mc” and keeping the phonetic sounding “Kray”, as was popular amongst Scots immigrants who wished their names to sound less Scottish in London, especially during the 18th century wars between Scotland and England under Bonnie Prince Charlie. This probably accounts for the instances of the name cropping up around Yorkshire, Durham, and Lancashire, thanks to their sea connections and industrial growth which brought in many Scots and Irish Sailors and industrial workers.
The last possibility is a German origin, as the name Kray is found amongst German immigrants to the UK and USA, and during the 18th century many German immigrants came to London on the back of the Hanoverian Georges becoming Kings of England, and Germans arrived both as craftsmen and as mercenaries to fight in the wars in America and Europe.
Whatever their origins we do know that by the beginning of the end of the 18th century the Kray family were established in the City of London and Middlesex by the Thames, in what would now be called Central London.