"Negative two floor" in Engpsh is commonly referred to as "Basement -2".
The origin of the term "basement" refers to the lower level of a building that is usually partially or completely below ground level, and the use of a negative number (-2) before "basement" simply indicates a level that is further below ground level.
Examples:
"I'll meet you in the lobby of the building and then we'll head down to the basement -2 to get to the parking lot."
(我们将在大楼的大厅见面，然后下楼到地下二层去停车场。)
"The storage room is located in the basement -2, next to the boiler room."
(储藏室位于地下二层，旁边是锅炉房。)