Sulfur

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Middle English: from Anglo-Norman French sulfre, from Latin sulfur, sulphur .

wiktionary

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From Middle English sulphur, borrowed from Anglo-Norman sulfre, from Latin sulfur, from sulpur itself of uncertain origin, but probably from Proto-Indo-European *swelplos, from the root *swel-(“to burn, smoulder”). Displaced Old English swefl and largely displaced brimstone.

etymonline

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sulfur (n.)

also sulphur, c. 1300, from Anglo-French sulfere, Old French soufre "sulfur, fire and brimstone, hellfire" (13c.), later also sulphur, from Late Latin sulfur, from Latin sulphur, probably from a root meaning "to burn." Ousted native brimstone and cognate Old English swefl, German schwefel, Swedish swafel, Dutch zwavel. The spelling with -ph- is standard in Britain, but its suggestion of a Greek origin is misleading.