To treat with sulphur or to infuse with sulphurous qualities.
From 'en-' plus 'sulphur', the chemical element. Medieval alchemists and physicians used this term when applying sulphur as a treatment or incorporating it into preparations.
Alchemists were obsessed with sulphur—they used 'ensulphur' to describe processes that would infuse something with sulphur's properties, believing it held mysterious transformative powers in both medicine and the quest to create gold.
Complete word intelligence in one call. Free tier — 50 lookups/day.