Underground railways are known, in the USA, as the subway.
Americans call them 'The Subway', the British call them 'The Underground' or 'The Tube'.
Subway
The underground rail system - what Americans would call a subway system.
they call it that because it was underground and its was a rail road
Dungeon
sewerage
Americans call a thong a thong.
An aquifer is an underground accumulation of water.
they call Americans Pigs
Americans call a tap a FAUCET. Your welcome!
tubers
they don't