Old French ametiste, amatiste, < Latin amethyst-us, < Greek ἀμέθυστ -ος, prop. adj. ‘not drunken’ ( < ἀ priv. + *μέθυστος, verbal adjective < μεθύσκ-ειν to intoxicate, < μέθυ wine: see mead n.1), applied subst. to this stone (as also to a herb), from a notion that it was a preventive of intoxication.It isn't clear to me how stones prevent intoxication, but never mind that. The French "amatist" form is dying to be misunderstood as "love-stone," which is more or less the exact opposite of the original etymology; the Philip Sidney quotation in the OED is a great example:
(I do not know how conscious the etymological joke is here, of course.)
The bloudy shaftes of Cupids warre,
With amatists they headed are.
2. Via Sarah Duff, Georgia O'Keeffe's eating habits:
[author of book on said habits] plays Mr Collins to O'Keeffe's Lady Catherine de Bourgh. While you and I might think O'Keeffe's "soup mix", a blend of powdered milk, soy flour, kelp and brewer's yeast, sounds vile, Wood will concede only that it has a "strong taste". Garlic sandwiches? Delicious. Yarrow tea? Spicy and soothing. A soup made from native weeds? Full of vitamins. (If this soup, when served, did not taste right, Miss O'Keeffe would announce that it had not been "made with love").---
See Wikipedia for more on "amethyst." The context of the Sidney quotation is also worth quoting; it appears in a very "conventionally" beautiful bit of descriptive verse, the "amatists" are purple because they are fingernails:
Ah woe is me, my woes renewe; Now course doth leade me to her hand. Of my first love the fatall band. Where whitenes dooth for ever sitte : Nature her selfe enameld it. For there with strange compaSi dooth lie Warme snow, moyst pearle, softe ivorie. There fall those Saphir-coloured brookesWhich conduit-like with curious crookes Sweete Ilands make in that sweete land. As for the fingers of the hand The bloudy shaftes of Cupids warre With amatists they headed are.