South End Green has been marked as such on maps since the 18th century, going simultaneously by another name - Pond Street.
The area took more shape along the rough edges of Hampstead Heath in 1835, when the small puddle at the bottom of aptly-named Pond Street was filled in. Much like Parliament Hill on the opposite side of the Heath, the arrival of a tram terminus brought people, shops, roads, homes and large public houses to this once sleepy hamlet by mid-century.