The common notion in all of the definitions of sluice is controlling the flow of water:
1.0 (also sluice gate) A sliding gate or other device for controlling the flow of water, especially one in a lock gate:
The water gushed through the sluices.
Lake levels are now regulated by sluices.
1.1 (also sluiceway) An artificial water channel for carrying off overflow or surplus water.
1.2 (In gold mining) a channel or trough constructed with grooves into which a current of water is directed in order to separate gold from the ore containing it.
2.0 An act of rinsing or showering with water:
1.0 Wash or rinse freely with a stream or shower of water:
She sluiced her face in cold water.
Crews sluiced down the decks of their ship
1.1 [NO OBJECT, WITH ADVERBIAL OF DIRECTION] (Of water) pour or flow freely:
The waves sluiced over them.
The etymology starts with the exclusion of water, but the usage extends from there:
c.1400, earlier scluse (mid-14c.), a shortening of Old French escluse
"sluice, floodgate" (Modern French écluse),
from Late Latin exclusa "barrier to shut out water" (in aqua exclusa
"water shut out," i.e. separated from the river),
from fem. singular of Latin exclusus, past participle of excludere "to
- The sluice gate is a tool to exclude water from places where it is undesirable.
- The sluiceway is also a tool to carry the water away (because water builds up behind obstacles unless it is carried away), simultaneously carrying water to a more desirable location.
- By extension, any act of intentionally moving water in an open channel is the verb sluice.
- By further extension, the water is carried to sluice gold ore, separating heavier gold particles from other sediment.
- By extension, any act of washing with running water is associated with sluice.
- By extension, [re]moving any extraneous material is a metaphorical sluice.