Iodine

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early 19th century: from French iode (from Greek iōdēs ‘violet-coloured’, from ion ‘violet’ + -eidēs ‘like’) + -ine4.

wiktionary

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From French iode + -ine, from Ancient Greek ἰοειδής(ioeidḗs, “violet”). Coined by British chemist Humphry Davy in 1814.

etymonline

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iodine (n.)

non-metallic element, 1814, formed by English chemist Sir Humphry Davy from French iode "iodine," which was coined 1812 by French chemist Joseph Louis Gay-Lussac from Greek ioeides "violet-colored" (from ion "the violet; dark blue flower;" see violet) + eidos "appearance" (see -oid).

Davy added the chemical suffix -ine (2) to make it analogous with chlorine and fluorine. So called from the color of the vapor given off when the crystals are heated.