Here's why it's called that:
* Sluice: This word refers to a channel or gate used to control the flow of water.
* House: This implies a dwelling, albeit a very basic and rundown one.
Therefore, "sluice-house" suggests a building that is:
* Damp and waterlogged: Perhaps near a river or marsh.
* Dirty and neglected: Like a place that's been forgotten or abandoned.
* Grim and forbidding: A place that wouldn't offer much comfort or safety.
The imagery of the "sluice-house" is important because it contrasts sharply with the elegance and respectability of Miss Havisham's house and reflects Pip's own journey from poverty to wealth and back again. It also serves as a symbol of the harsh realities of Pip's world and the dangers that lurk beneath the surface of Victorian society.