In answer to your question, Richard.
It has been said that during the 'Black Death' c1350, it was where the plague fizzled out, hence the graves ended. Not too sure of that?
We do say it as two words - - Graves End.
But I think the web provides a more reliable source, here are a couple of extracts:-
Gravesend comes from the Old English 'grāf' meaning a 'grove, copse' with 'ende' as an 'end, the end of something'; therefore, 'end of the grove'. The Domesday Book records Gravesend as Gravesham and the Textus Roffensis as Gravesaende
Gravesend was once one of the most important ports in England, given the sole rights to transporting passengers to and from London in the 14th century. During the 19th century, steamboats chugged up and down the river and thousands of immigrants disembarked in the town as the first port on the Thames
As you are frequently referring to our past criminals, read on:-Crime and Safety in Gravesend, Kent. I will not enter into my political slant on this - but - I'll just say the police warned have people to go careful in the town, although crime is spreading to the suburbs. A sign of our times perhaps?
Gravesend is among the top 5 most dangerous medium-sized towns in Kent, and is the 21st most dangerous overall out of Kent's 335 towns, villages, and cities. The overall crime rate in Gravesend in 2020 was 117 crimes per 1,000 people.