What is the name used for this type of connectors?

Twin port connection. Usually for voltages under 25Vdc. It also has a restrictor edge to ensure it can only connect one way... the correct circuit designed way.

Try the search term water proof or water resistance connectors for electric bikes.

Here is similar Electric Bike Connector

Here another similar connector used in Electric Bikes

Here is similar connector from e-bay

Looks like the supplier name is Higo Waterproof Connectors

Also take a look at Korean Cable and Components. They are based in Germany.

Another connector from Aohua

2 Pin Waterproof Led Cable Connector Ip65 For Light Bar

References:

• Shenzhen Aohua Electric Corporation