The word 'sulfur' entered English in the late 14th century from the Anglo-French 'sulfre' and the Latin 'sulfur, sulphur'. The Latin term is believed to be of pre-Latin, possibly Italic, origin. While the exact Proto-Indo-European source is obscure, it is a very ancient word for the substance, unrelated to Greek 'theion' (which gave us the prefix 'thio-'). The spelling has alternated historically between 'sulfur' and 'sulphur', with 'sulfur' being the standard in scientific and American English, reflecting the original Latin form.

The word is a simplex loanword from Latin. It cannot be meaningfully segmented into productive morphemes within modern English spelling.