leach

Etymology 1

From Middle English leche (“leachate; sluggish stream”), from Old English *lǣċ, *lǣċe (“muddy stream”), from Proto-Germanic *lēkijō (“a leak, drain, flow”) (compare Proto-Germanic *lekaną (“to leak, drain”)), from Proto-Indo-European *leǵ- (“to leak”). Cognate with Old English leċċan (“to water, moisten”), Old English lacu (“stream, pool, pond”). More at leak, lake.

noun

1. A quantity of wood ashes, through which water passes, and thus imbibes the alkali.
2. A tub or vat for leaching ashes, bark, etc.
   "This is the leach," said Kitty, pointing to a large, yellowish, upright wooden cylinder, which rested on some slanting boards, down the surface of which ran a brownish liquid that dripped into a trough. 1894, Robert Barr, chapter 7, in In the Midst of Alarms
3. (nautical) Alternative spelling of leech.
4. A jelly-like sweetmeat popular in the fifteenth century.
   1670, Hannah Woolley, “To make Leach and to colour it”, in The Queen-like Closet, Or, Rich Cabinet:

Etymology 2

From Middle English *lechen, *lecchen, from Old English leċċan, from Proto-Germanic *lakjaną, from Proto-Indo-European *leǵ- (“to leak”).

verb

1. (transitive) To purge a soluble matter out of something by the action of a percolating fluid.
   Heavy rainfall can leach out minerals important for plant growth from the soil.
   [T]he very wet winter will have washed much of the goodness out of the soil. Homemade compost and the load of manure we get from a friendly farmer may not be enough to compensate for what has leached from the ground. 21 April 2014, Mary Keen, “You can still teach an old gardener new tricks: Even the hardiest of us gardeners occasionally learn useful new techniques [print version: Gardening is always ready to teach even the hardiest of us a few new tricks, 19 April 2014]”, in The Daily Telegraph (Gardening), page G7
2. (intransitive) To part with soluble constituents by percolation.
   The gangue was leached to recover minerals left behind by the original technology.
3. (figurative, intransitive) To bleed, seep.
   A more generic geography, one where the suburb uneasily abuts the commercial and industrial, or leaches out to a nonurban frontier. 2007, Andrew Shanken, “The Sublime "Jackass"”, in Places, volume 19