magnet n.

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.

"a very hard stone," mid-14c., adamant, adamaunt, from Old French adamant "diamond; magnet" or directly from Latin adamantem (nominative adamas) "adamant, hardest iron, steel," also used figuratively, of character, from Greek adamas (genitive adamantos), the name of a hypothetical hardest material.

It is a noun use of an adjective meaning "unbreakable, inflexible," which was metaphoric of anything unalterable (such as Hades) and is of uncertain origin. 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)," for which 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]. The word had been in Old English as aðamans, but the modern word is a re-borrowing.