Etymology
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pile (v.)

"to heap (up), lay or throw in a heap," c. 1400, from pile (n.1). Related: Piled; piling. Figurative verbal phrase pile on "attack vigorously, attack en masse," is attested by 1894, American English. To pile in "climb or go on or into in a crowd" is by 1841; hence, for the reverse process, pile out, by 1896.

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junk (v.)

1803, "to cut off in lumps," from junk (n.1). The meaning "to throw away as trash, to scrap" is from 1908. Related: Junked; junking.

New settlers (who should always be here as early in the spring as possible) begin to cut down the wood where they intend to erect their first house. As the trees are cut the branches are to be lopped off, and the trunks cut into lengths of 12 or 14 feet. This operation they call junking them; if they are not junked before fire is applied, they are much worse to junk afterwards. [letter dated Charlotte Town, Nov. 29, 1820, in "A Series of Letters Descriptive of Prince Edward Island," 1822]
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junk (n.2)
"large, seagoing Chinese sailing ship," 1610s, from Portuguese junco, from Malay (Austronesian) jong "ship, large boat" (13c.), probably from Javanese djong. In English 16c. as giunche, iunco.
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junk (n.1)

mid-14c., junke "old cable or rope," cut in bits and used for caulking, etc., a nautical word of uncertain origin, perhaps from Old French junc "rush, reed," also used figuratively as a type of something of little value, from Latin iuncus "rush, reed" (but OED finds "no evidence of connexion").

It was extended to "old refuse from boats and ships" (1660s), then to "old or discarded articles of any kind" (1884), usually with a suggestion of reusability. Meaning "salt meat used on long voyages" is from 1762. Meaning "narcotic drug" is from 1925. Junk food is from 1971; junk art is from 1961; junk mail first attested 1954; junk bond from 1979.

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pile (n.1)

early 15c., "heap or stack of something," usually consisting of an indefinite number of separate objects arranged in a more or less regular conical or pyramidal form, from Old French pile "a heap, a stack," and directly from Latin pila "a pillar," also "stone barrier, pier" (see pillar).

The sense development in Latin would have been from "pier, harbor wall of stones," to "something heaped up." Middle English pile also could mean "pillar supporting something, pier of a bridge" (mid-15c.).  In English, the verb in the sense of "to heap (up)" is recorded from c.1400.

Middle English also had a noun pile meaning "castle, tower, stronghold (late 14c.), which persisted in a sense of "large building." OED regards this as a separate word, of doubtful origin, but other sources treat them as the same.

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pile (n.2)

late Old English pil "sharp stake or stick," also, poetically, "arrow, dart," from Latin pilum, the name of the heavy javelin of the Roman foot soldier (source of Old Norse pila, Old High German pfil, German Pfeil "arrow"), a word of uncertain origin. De Vaan finds the identification of it with the pilum that means "pestle, pounder" (from *pis-tlo-, from the root of pinsere "to crush, pound;" see pestle) to be defensible.

In engineering and architecture, "a heavy timber beam, pointed or not, driven into the soil for support of a structure or as part of a wall." It also has meant "pointed head of a staff, pike, arrow, etc." (1590s) and the word is more or less confused with some of the sense under pile (n.1).

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pile (n.3)

mid-14c., "downy plumage;" late 15c, "fine, soft hair," from Anglo-French pyle or Middle Dutch pijl, both from Latin pilus "a hair" (source of Italian pelo, Old French pel), a word of uncertain origin. Phonological evidence rules out transmission of the English word via Old French cognate peil, poil. Meaning "soft, raised surface of a regular and closely set kind upon cloth" is from 1560s.

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pile-up (n.)

"multi-vehicle crash," 1929, from verbal phrase pile up "to heap up" (c. 1400), which is attested from 1849 as "to accumulate," 1899 as "to wreck in a heap" (see pile (v.)).

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junk-shop (n.)
1800, "marine shop," from junk (n.1) in the sense "discarded articles from ships." By 1951 in the non-marine sense "junk-dealer."
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pile-driver (n.)

1772 in literal sense, "machine for driving piles," from pile (n.2) + driver. Figurative sense of "very strong hit" is recorded from 1858.

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