Why is the Apex Corner roundabout called Apex Corner?

Northway Circus is the notoriously busy roundabout in north London that you have never heard of because you’ll know it by its nickname, Apex Corner.
But why is Northway Circus better known as Apex Corner?
Quite a few businesses around it use the Apex name, but they’re all named after the roundabout, not the other way around. There’s nothing locally called Apex, and old maps show the area as Gibbs Green, so there’s nothing to explain how Northway Circus gained its nickname