A long time ago, of troy twice mentioned, but apparently never found the origin of the term
"bain marie". I stumbled on it today in "engines of our ingenuity". It's in the last lines of:

The great chemist Maria the Jewess has been
pretty well lost in the blur of ancient history. Most
of what we know about her comes from the Egyptian
alchemist Zosimos, who wrote in the late days of the
Roman empire, 500 years after Maria lived. Among
other things, Zosimos talks about her invention of the
kerotakis.

Maria invented many types of stills and reflux
condensers. The kerotakis device was one in which
she could boil mercury or sulfur and use its
condensing vapor to heat copper or lead in a pan
above. It was a kind of high-temperature double
boiler.

Remember how a double boiler works: It has an
upper pan where you cook food, nested in a lower
pan of boiling water. The food stays at the same
temperature as the steam condensing under it -- 100
degrees C. And so the one reference to Maria in the
modern world is the French word for a double
boiler. They call it a bain-marie -- Maria's bath.