Heater cartridge connector for Original Prusa i3 MK2S
This is referred to as a Terminal Block Connector.   More specifically this is a 2-position pluggable terminal block connector commonly manufactured by Phoenix Contact and others.

Newark.com Sale Page: Pluggable Terminal Block, 5.08 mm, 2 Positions, 24 AWG, 12 AWG, 2.5 mm², Screw 

Larger Picture: 2-Position Terminal Block Connectors