Is it one of those cubes used to connect 2 pairs of mains wires, like when you install a ceiling light? When you look at it from the top it has 4 screws, i'm not sure about the name in english.
Back to pc ..... Benm wins again ..... it's called "mammuth", here (don't ask me why, i never discovered this ), and it's a connection block for 2 wires (seen from bottom).