early 12c., ungeon, oinyon, unione, "the underground bulb of the common onion plant," from Anglo-French union, Old French oignon "onion" (formerly also oingnon), and directly from Latin unionem (nominative unio), a colloquial rustic Roman word for a kind of onion, also "pearl" (via the notion of a string of onions), literally "one, unity." The sense connection is the unity of the successive layers of an onion, in contrast with garlic or cloves.
Old English had ynne (in ynne-leac), from the same Latin source, which also produced Irish inniun, Welsh wynwyn and similar words in Germanic. In Dutch, the ending in -n was mistaken for a plural inflection and new singular ui formed. The usual Indo-European name is represented by Greek kromion, Irish crem, Welsh craf, Old English hramsa, Lithuanian kermušė.
The usual Latin word was cepa, a loan from an unknown language; it is the source of Old French cive, Old English cipe, and, via Late Latin diminutive cepulla, Italian cipolla, Spanish cebolla, Polish cebula. German Zwiebel also is from this source, but altered by folk etymology in Old High German (zwibolla) from words for "two" and "ball."
Onion-ring "circular segment of an onion" (especially battered and deep-fried) is attested by 1904. Onion-dome on a church-tower, etc., is attested by 1950, so called for the resemblance of shape; onion-grass, which forms tuberous nodes in its roots (also onion-couch) is from 1823; onion-skin as a type of paper (so called for its thinness, transparency, and finish, which resemble the skin of an onion) is from 1879.
Onions, the surname, is attested from mid-12c. (Ennian), from Old Welsh Enniaun, ultimately from Latin Annianus, which was associated with Welsh einion "anvil."
also dumbbell, "one of a pair of weighted bars used for exercise," by 1785, earlier (from 1711), according to OED, an apparatus like that used to ring a church bell, but without the bell (hence dumb); used for physical exercise but sometimes also to practice ringing changes. See dumb (adj.) + bell (n.). If this is right, the word must have been transferred; earlier 18c. references make mention of "pulling" or "ringing" dumb-bells and note that it can be done only indoors. The following is a footnote to the 1903 reprint of Joseph Strutt's 1801 "The Sports and Pastimes of the People of England":
The origin of the term is somewhat curious. Dumb-bells take their name by analogy, as was pointed out in Notes and Queries in 1861, "from a machine used for exercise, consisting of a rough, heavy, wooden flywheel with a rope passing through and round a spindle ... and set in motion like a church bell." This statement, however, does not sufficiently explain the transference of such a name to the short bar and rounded lead or iron ends of a hand dumb-bell. This difficulty was explained by the late Chancellor Ferguson in a paper read before the Archaeological Institute in 1895, wherein a dumb-bell apparatus, now at Lord Sackville's seat at Knowle, was described and illustrated. The roller round which the rope winds and unwinds has four iron arms, each of which has a leaden poise or ball at the end, just like the end of an ordinary hand dumb-bell. This Knowle example is fixed in an attic and the rope passed through to a gallery beneath. Anyone pulling the rope would get much the same exercise as in pulling a bell rope in a church tower, but without annoying his neighbours by the noise. There used to be a similar apparatus at New College, Oxford.
Figurative sense of "blockhead, stupid person" attested by 1918, American English college slang.
c. 1300, fairie, "the country or home of supernatural or legendary creatures; fairyland," also "something incredible or fictitious," from Old French faerie "land of fairies, meeting of fairies; enchantment, magic, witchcraft, sorcery" (12c.), from fae "fay," from Latin fata "the Fates," plural of fatum "that which is ordained; destiny, fate," from PIE root *bha- (2) "to speak, tell, say." Also compare fate (n.), also fay.
In ordinary use an elf differs from a fairy only in generally seeming young, and being more often mischievous. [Century Dictionary]
But that was before Tolkien. As a type of supernatural being from late 14c. [contra Tolkien; for example "This maketh that ther been no fairyes" in "Wife of Bath's Tale"], perhaps via intermediate forms such as fairie knight "supernatural or legendary knight" (c. 1300), as in Spenser, where faeries are heroic and human-sized. As a name for the diminutive winged beings in children's stories from early 17c.
Yet I suspect that this flower-and-butterfly minuteness was also a product of "rationalization," which transformed the glamour of Elfland into mere finesse, and invisibility into a fragility that could hide in a cowslip or shrink behind a blade of grass. It seems to become fashionable soon after the great voyages had begun to make the world seem too narrow to hold both men and elves; when the magic land of Hy Breasail in the West had become the mere Brazils, the land of red-dye-wood. [J.R.R. Tolkien, "On Fairy-Stories," 1947]
Hence, figurative adjective use in reference to lightness, fineness, delicacy. Slang meaning "effeminate male homosexual" is recorded by 1895. Fairy ring, of certain fungi in grass fields (as we would explain it now), is from 1590s. Fairy godmother attested from 1820. Fossil Cretaceous sea urchins found on the English downlands were called fairy loaves, and a book from 1787 reports that "country people" in England called the stones of the old Roman roads fairy pavements.