"variety of magnetite characterized by its power of attracting iron and steel," mid-15c. (earlier magnes, late 14c.), from Old French magnete "magnetite, magnet, lodestone," and directly from Latin magnetum (nominative magnes) "lodestone," from Greek ho Magnes lithos "the Magnesian stone," from Magnesia (see magnesia), region in Thessaly where magnetized ore was obtained. Figurative sense of "something which attracts" is from 1650s.
It has spread from Latin to most Western European languages (German and Danish magnet, Dutch magneet, Italian, Spanish, Portuguese magnete), but it was superseded in French by aimant (from Latin adamas; see adamant (n.)). Italian calamita "magnet" (13c.), French calamite (by 16c., said to be from Italian), Spanish caramida (15c., probably from Italian) apparently is from Latin calamus "reed, stalk or straw of wheat" (see shawm) "the needle being inserted in a stalk or piece of cork so as to float on water" [Donkin]. Chick magnet attested from 1989.
1610s, "the characteristic properties of a magnet," from Modern Latin magnetismus (see magnet + -ism). Figurative sense of "personal charm, attractive power or influence" is from 1650s; in the hypnotic sense it is from Mesmer (see mesmerism). Meaning "science of magnets and magnetic phenomena" is by early 19c.
1610s, literal, "having the properties of a magnet;" 1630s, figurative, "having powers of attraction;" from Modern Latin magneticus, from Latin magnes (see magnet). Meaning "capable of being attracted by a magnet" is by 1837. Related: Magnetical (1580s); magnetics "the science of magnetism" (1786).
late 14c., in alchemy, "one of the two main ingredients of the philosopher's stone," from Medieval Latin magnesia, from Greek (he) Magnesia (lithos) "the lodestone," literally "(the) Magnesian (stone)," a mineral said to have been brought from Magnesia, the region in Thessaly, which is said to be named for the native people name Magnetes, which is of unknown origin.
The ancient word, in this sense, has evolved into magnet. But in ancient times the same word, magnes, was used of lodestone as well as of a mineral commonly used in bleaching glass (modern pyrolusite, or manganese dioxide).
In the Middle Ages there was some attempt to distinguish lodestone as magnes (masc.) and pyrolusite as magnesia (fem.). Meanwhile, in 18c., a white powder (magnesium carbonate) used as a cosmetic and toothpaste was sold in Rome as magnesia alba ("white magnesia").
It was from this last, in 1808, that Davy isolated magnesium. He wanted to call it magnium, to stay as far as possible from the confused word magnesia, but the name was adopted in the form magnesium. Meanwhile from 16c. the other name of pyrolusite had been corrupted to manganese, and when, in 1774, a new element was isolated from it, it came to be called manganese.
Magnesia in its main modern sense of "magnesium oxide" (1755) is perhaps an independent formation from Modern Latin magnes carneus "flesh-magnet" (c. 1550), so called because it adheres strongly to the lips.
It is perhaps literally "invincible, indomitable," from a- "not" (see a- (3)) + daman "to conquer, to tame," from PIE root *deme- "to constrain, force, break (horses)" (see tame (adj.)). "But semantically, the etymology is rather strange," according to Beekes, who suggests it might be a foreign word altered in Greek by folk etymology, and compares Akkadian (Semitic) adamu.
Applied in antiquity to a metal resembling gold (Plato), white sapphire (Pliny), magnet (Ovid, perhaps through confusion with Latin adamare "to love passionately"), steel, emery stone, and especially diamond, which is a variant of this word. "The name has thus always been of indefinite and fluctuating sense" [Century Dictionary].