athanor
A furnace or stove designed and used to maintain uniform heat, primarily used by alchemists.
historical
You may also be inſtructed, That when you are diſtilling of Aqua fort. and that the Coals in the Athanor are almoſt gone out (which happens hardly in 10 or 11 hours) then lift up the Cover from the Athanor, make it full again with Coals and cover it, elſe the Fire will go out, and all will be cold, as Oportunity it ſelf will teach thee and make thee to remember.
Where it comes from
From Arabic التَنُّور (at-tannūr, “the baker’s oven”). The word is a doublet of tandoor.
Adapted from the Wiktionary entry athanor (CC BY-SA 4.0).