sluice

What it means

1. An artificial passage for water, fitted with a valve or gate, for example in a canal lock or a mill stream, for stopping or regulating the flow.
2. A water gate or floodgate.
3. Hence, an opening or channel through which anything flows; a source of supply.

   Each sluice of affluent fortune open'd soon.

   1767, Walter Harte, Eulogius: Or, The Charitable Mason

   2 more examples

   At leaſt, I'm ſure I can fiſh it out of her. She's the very Sluce to her Lady's Secrets;—'Tis but ſetting her Mill agoing, and I can drein her of 'em all.

   1693, Will[iam] Congreve, The Old Batchelour, a Comedy. […], London: […] Peter Buck, […], →OCLC, Act V, scene i, page 45

   This home familiarity […] opens the sluices of sensibility.

   1832, [Isaac Taylor], Saturday Evening. […], London: Holdsworth and Ball, →OCLC

In a sentence

At leaſt, I'm ſure I can fiſh it out of her. She's the very Sluce to her Lady's Secrets;—'Tis but ſetting her Mill agoing, and I can drein her of 'em all.

1693, Will[iam] Congreve, The Old Batchelour, a Comedy. […], London: […] Peter Buck, […], →OCLC, Act V, scene i, page 45

Where it comes from

1. Latinexclūsus
2. Late Latinexclusa“extrusion, gate”
3. Anglo-Normanescluse“sluice, floodgate”
4. Middle Englishsluse
5. Englishsluice

From Middle English sluse, alteration of scluse, from Anglo-Norman escluse (“sluice, floodgate”), from Late Latin exclusa (“extrusion, gate”), from Latin exclūsus, form of exclūdō (“to shut out, to exclude”) (English exclude). Cognate to Dutch sluis.