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.

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).

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.

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.

Definitions of pile
pile (n.)
a collection of objects laid on top of each other;
pile (n.)
(often followed by `of') a large number or amount or extent;
Synonyms: batch / deal / flock / good deal / great deal / hatful / heap / lot / mass / mess / mickle / mint / mountain / muckle / passel / peck / plenty / pot / quite a little / raft / sight / slew / spate / stack / tidy sum / wad
pile (n.)
a large sum of money (especially as pay or profit);
Synonyms: bundle / big bucks / megabucks / big money
pile (n.)
fine soft dense hair (as the fine short hair of cattle or deer or the wool of sheep or the undercoat of certain dogs);
Synonyms: down
pile (n.)
battery consisting of voltaic cells arranged in series; the earliest electric battery devised by Volta;
Synonyms: voltaic pile / galvanic pile
pile (n.)
a column of wood or steel or concrete that is driven into the ground to provide support for a structure;
Synonyms: spile / piling / stilt
pile (n.)
the yarn (as in a rug or velvet or corduroy) that stands up from the weave;
for uniform color and texture tailors cut velvet with the pile running the same direction
Synonyms: nap
pile (n.)
a nuclear reactor that uses controlled nuclear fission to generate energy;
Synonyms: atomic pile / atomic reactor / chain reactor
pile (v.)
arrange in stacks;
Synonyms: stack / heap
pile (v.)
press tightly together or cram;
Synonyms: throng / mob / pack / jam
pile (v.)
place or lay as if in a pile;
The teacher piled work on the students until the parents protested