For those learning French who might be puzzled by the spelling, the correct french word for something underground is "souterrain" (it is also a noun for an unde

For those learning French who might be puzzled by the spelling, the correct french word for something underground is "souterrain" (it is also a noun for an underground tunnel). Probably they chose that spelling to suggest that it is not cargo buried underground, or something illegal (there's that meaning too, like "underground economy": économie souterraine).